[PATCH 0/9] built-in add -p: add support for the same config settings as the Perl version

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53 messages, 5 authors, 2020-01-17 · open the first message on its own page

[PATCH 0/9] built-in add -p: add support for the same config settings as the Perl version

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:04

This is the final leg of the journey to a fully built-in git add: the git
add -i and git add -p modes were re-implemented in C, but they lacked
support for a couple of config settings.

The one that sticks out most is the interactive.singleKey setting: it was
particularly hard to get to work, especially on Windows.

It also seems to be the setting that is incomplete already in the Perl
version of the interactive add command: while the name of the config setting
suggests that it applies to all of the interactive add, including the main
loop of git add --interactive and to the file selections in that command, it
does not. Only the git add --patch mode respects that setting.

As it is outside the purpose of the conversion of git-add--interactive.perl 
to C, we will leave that loose end for some future date.

Johannes Schindelin (9):
  built-in add -p: support interactive.diffFilter
  built-in add -p: handle diff.algorithm
  terminal: make the code of disable_echo() reusable
  terminal: accommodate Git for Windows' default terminal
  terminal: add a new function to read a single keystroke
  built-in add -p: respect the `interactive.singlekey` config setting
  built-in add -p: handle Escape sequences in interactive.singlekey mode
  built-in add -p: handle Escape sequences more efficiently
  ci: include the built-in `git add -i` in the `linux-gcc` job

 add-interactive.c         |  19 +++
 add-interactive.h         |   4 +
 add-patch.c               |  57 ++++++++-
 ci/run-build-and-tests.sh |   1 +
 compat/terminal.c         | 249 +++++++++++++++++++++++++++++++++++++-
 compat/terminal.h         |   3 +
 6 files changed, 325 insertions(+), 8 deletions(-)


base-commit: 2d4b85ddc76af3e703e6e3a6a72319b5e79c2d8b
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-175%2Fdscho%2Fadd-p-in-c-config-settings-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-175/dscho/add-p-in-c-config-settings-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/175
-- 
gitgitgadget

[PATCH 1/9] built-in add -p: support interactive.diffFilter

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:11

From: Johannes Schindelin <redacted>

The Perl version supports post-processing the colored diff (that is
generated in addition to the uncolored diff, intended to offer a
prettier user experience) by a command configured via that config
setting, and now the built-in version does that, too.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 12 ++++++++++++
 add-interactive.h |  3 +++
 add-patch.c       | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index 0e753d2acc..00c3bc9a1b 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -52,6 +52,17 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 		diff_get_color(s->use_color, DIFF_FILE_OLD));
 	init_color(r, s, "new", s->file_new_color,
 		diff_get_color(s->use_color, DIFF_FILE_NEW));
+
+	FREE_AND_NULL(s->interactive_diff_filter);
+	git_config_get_string("interactive.difffilter",
+			      &s->interactive_diff_filter);
+}
+
+void clear_add_i_state(struct add_i_state *s)
+{
+	FREE_AND_NULL(s->interactive_diff_filter);
+	memset(s, 0, sizeof(*s));
+	s->use_color = -1;
 }
 
 /*

@@ -1149,6 +1160,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	strbuf_release(&print_file_item_data.worktree);
 	strbuf_release(&header);
 	prefix_item_list_clear(&commands);
+	clear_add_i_state(&s);
 
 	return res;
 }

diff --git a/add-interactive.h b/add-interactive.h
index 4895ed1df5..7299cf6e04 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -15,9 +15,12 @@ struct add_i_state {
 	char context_color[COLOR_MAXLEN];
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
+
+	char *interactive_diff_filter;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);
+void clear_add_i_state(struct add_i_state *s);
 
 struct repository;
 struct pathspec;

diff --git a/add-patch.c b/add-patch.c
index 2ad18dc3cb..73bf2caca2 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -397,6 +397,7 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 
 	if (want_color_fd(1, -1)) {
 		struct child_process colored_cp = CHILD_PROCESS_INIT;
+		const char *diff_filter = s->s.interactive_diff_filter;
 
 		setup_child_process(s, &colored_cp, NULL);
 		xsnprintf((char *)args.argv[color_arg_index], 8, "--color");

@@ -406,6 +407,24 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		argv_array_clear(&args);
 		if (res)
 			return error(_("could not parse colored diff"));
+
+		if (diff_filter) {
+			struct child_process filter_cp = CHILD_PROCESS_INIT;
+
+			setup_child_process(s, &filter_cp,
+					    diff_filter, NULL);
+			filter_cp.git_cmd = 0;
+			filter_cp.use_shell = 1;
+			strbuf_reset(&s->buf);
+			if (pipe_command(&filter_cp,
+					 colored->buf, colored->len,
+					 &s->buf, colored->len,
+					 NULL, 0) < 0)
+				return error(_("failed to run '%s'"),
+					     diff_filter);
+			strbuf_swap(colored, &s->buf);
+		}
+
 		strbuf_complete_line(colored);
 		colored_p = colored->buf;
 		colored_pend = colored_p + colored->len;

@@ -530,6 +549,9 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 						   colored_pend - colored_p);
 			if (colored_eol)
 				colored_p = colored_eol + 1;
+			else if (p != pend)
+				/* colored shorter than non-colored? */
+				goto mismatched_output;
 			else
 				colored_p = colored_pend;

@@ -554,6 +576,15 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		 */
 		hunk->splittable_into++;
 
+	/* non-colored shorter than colored? */
+	if (colored_p != colored_pend) {
+mismatched_output:
+		error(_("mismatched output from interactive.diffFilter"));
+		advise(_("Your filter must maintain a one-to-one correspondence\n"
+			 "between its input and output lines."));
+		return -1;
+	}
+
 	return 0;
 }

@@ -1611,6 +1642,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	    parse_diff(&s, ps) < 0) {
 		strbuf_release(&s.plain);
 		strbuf_release(&s.colored);
+		clear_add_i_state(&s.s);
 		return -1;
 	}

@@ -1629,5 +1661,6 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	strbuf_release(&s.buf);
 	strbuf_release(&s.plain);
 	strbuf_release(&s.colored);
+	clear_add_i_state(&s.s);
 	return 0;
 }

-- 
gitgitgadget

[PATCH 2/9] built-in add -p: handle diff.algorithm

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:12

From: Johannes Schindelin <redacted>

The Perl version of `git add -p` reads the config setting
`diff.algorithm` and if set, uses it to generate the diff using the
specified algorithm.

This patch ports that functionality to the C version.

Note: just like `git-add--interactive.perl`, we do _not_ respect this
config setting in `git add -i`'s `diff` command, but _only_ in the
`patch` command.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 5 +++++
 add-interactive.h | 2 +-
 add-patch.c       | 3 +++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/add-interactive.c b/add-interactive.c
index 00c3bc9a1b..77762d75d6 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -56,11 +56,16 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	FREE_AND_NULL(s->interactive_diff_filter);
 	git_config_get_string("interactive.difffilter",
 			      &s->interactive_diff_filter);
+
+	FREE_AND_NULL(s->interactive_diff_algorithm);
+	git_config_get_string("diff.algorithm",
+			      &s->interactive_diff_algorithm);
 }
 
 void clear_add_i_state(struct add_i_state *s)
 {
 	FREE_AND_NULL(s->interactive_diff_filter);
+	FREE_AND_NULL(s->interactive_diff_algorithm);
 	memset(s, 0, sizeof(*s));
 	s->use_color = -1;
 }

diff --git a/add-interactive.h b/add-interactive.h
index 7299cf6e04..21389851aa 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -16,7 +16,7 @@ struct add_i_state {
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
 
-	char *interactive_diff_filter;
+	char *interactive_diff_filter, *interactive_diff_algorithm;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);

diff --git a/add-patch.c b/add-patch.c
index 73bf2caca2..fdfaa76c3c 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -359,6 +359,7 @@ static int is_octal(const char *p, size_t len)
 static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 {
 	struct argv_array args = ARGV_ARRAY_INIT;
+	const char *diff_algorithm = s->s.interactive_diff_algorithm;
 	struct strbuf *plain = &s->plain, *colored = NULL;
 	struct child_process cp = CHILD_PROCESS_INIT;
 	char *p, *pend, *colored_p = NULL, *colored_pend = NULL, marker = '\0';

@@ -368,6 +369,8 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 	int res;
 
 	argv_array_pushv(&args, s->mode->diff);
+	if (diff_algorithm)
+		argv_array_pushf(&args, "--diff-algorithm=%s", diff_algorithm);
 	if (s->revision) {
 		struct object_id oid;
 		argv_array_push(&args,

-- 
gitgitgadget

[PATCH 6/9] built-in add -p: respect the `interactive.singlekey` config setting

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:12

From: Johannes Schindelin <redacted>

The Perl version of `git add -p` supports this config setting to allow
users to input commands via single characters (as opposed to having to
press the <Enter> key afterwards).

This is an opt-in feature because it requires Perl packages
(Term::ReadKey and Term::Cap, where it tries to handle an absence of the
latter package gracefully) to work. Note that at least on Ubuntu, that
Perl package is not installed by default (it needs to be installed via
`sudo apt-get install libterm-readkey-perl`), so this feature is
probably not used a whole lot.

In C, we obviously do not have these packages available, but we just
introduced `read_single_keystroke()` that is similar to what
Term::ReadKey provides, and we use that here.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c |  2 ++
 add-interactive.h |  1 +
 add-patch.c       | 21 +++++++++++++++++----
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index 77762d75d6..01a2f92f0c 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -60,6 +60,8 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	FREE_AND_NULL(s->interactive_diff_algorithm);
 	git_config_get_string("diff.algorithm",
 			      &s->interactive_diff_algorithm);
+
+	git_config_get_bool("interactive.singlekey", &s->use_single_key);
 }
 
 void clear_add_i_state(struct add_i_state *s)

diff --git a/add-interactive.h b/add-interactive.h
index 21389851aa..3450359685 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -16,6 +16,7 @@ struct add_i_state {
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
 
+	int use_single_key;
 	char *interactive_diff_filter, *interactive_diff_algorithm;
 };

diff --git a/add-patch.c b/add-patch.c
index fdfaa76c3c..ef0469d398 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -6,6 +6,7 @@
 #include "pathspec.h"
 #include "color.h"
 #include "diff.h"
+#include "compat/terminal.h"
 
 enum prompt_mode_type {
 	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK

@@ -1148,14 +1149,27 @@ static int run_apply_check(struct add_p_state *s,
 	return 0;
 }
 
+static int read_single_character(struct add_p_state *s)
+{
+	if (s->s.use_single_key) {
+		int res = read_key_without_echo(&s->answer);
+		printf("%s\n", res == EOF ? "" : s->answer.buf);
+		return res;
+	}
+
+	if (strbuf_getline(&s->answer, stdin) == EOF)
+		return EOF;
+	strbuf_trim_trailing_newline(&s->answer);
+	return 0;
+}
+
 static int prompt_yesno(struct add_p_state *s, const char *prompt)
 {
 	for (;;) {
 		color_fprintf(stdout, s->s.prompt_color, "%s", _(prompt));
 		fflush(stdout);
-		if (strbuf_getline(&s->answer, stdin) == EOF)
+		if (read_single_character(s) == EOF)
 			return -1;
-		strbuf_trim_trailing_newline(&s->answer);
 		switch (tolower(s->answer.buf[0])) {
 		case 'n': return 0;
 		case 'y': return 1;

@@ -1395,9 +1409,8 @@ static int patch_update_file(struct add_p_state *s,
 			      _(s->mode->prompt_mode[prompt_mode_type]),
 			      s->buf.buf);
 		fflush(stdout);
-		if (strbuf_getline(&s->answer, stdin) == EOF)
+		if (read_single_character(s) == EOF)
 			break;
-		strbuf_trim_trailing_newline(&s->answer);
 
 		if (!s->answer.len)
 			continue;

-- 
gitgitgadget

[PATCH 8/9] built-in add -p: handle Escape sequences more efficiently

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:12

From: Johannes Schindelin <redacted>

When `interactive.singlekey = true`, we react immediately to keystrokes,
even to Escape sequences (e.g. when pressing a cursor key).

The problem with Escape sequences is that we do not really know when
they are done, and as a heuristic we poll standard input for half a
second to make sure that we got all of it.

While waiting half a second is not asking for a whole lot, it can become
quite annoying over time, therefore with this patch, we read the
terminal capabilities (if available) and extract known Escape sequences
from there, then stop polling immediately when we detected that the user
pressed a key that generated such a known sequence.

This recapitulates the remaining part of b5cc003253c8 (add -i: ignore
terminal escape sequences, 2011-05-17).

Note: We do *not* query the terminal capabilities directly. That would
either require a lot of platform-specific code, or it would require
linking to a library such as ncurses.

Linking to a library in the built-ins is something we try very hard to
avoid (we even kicked the libcurl dependency to a non-built-in remote
helper, just to shave off a tiny fraction of a second from Git's startup
time). And the platform-specific code would be a maintenance nightmare.

Even worse: in Git for Windows' case, we would need to query MSYS2
pseudo terminals, which `git.exe` simply cannot do (because it is
intentionally *not* an MSYS2 program).

To address this, we simply spawn `infocmp -L -1` and parse its output
(which works even in Git for Windows, because that helper is included in
the end-user facing installations).

This is done only once, as in the Perl version, but it is done only when
the first Escape sequence is encountered, not upon startup of `git add
-i`; This saves on startup time, yet makes reacting to the first Escape
sequence slightly more sluggish. But it allows us to keep the
terminal-related code encapsulated in the `compat/terminal.c` file.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index b7f58d1781..35bca03d14 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -4,6 +4,7 @@
 #include "strbuf.h"
 #include "run-command.h"
 #include "string-list.h"
+#include "hashmap.h"
 
 #if defined(HAVE_DEV_TTY) || defined(GIT_WINDOWS_NATIVE)

@@ -238,6 +239,71 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+/*
+ * The `is_known_escape_sequence()` function returns 1 if the passed string
+ * corresponds to an Escape sequence that the terminal capabilities contains.
+ *
+ * To avoid depending on ncurses or other platform-specific libraries, we rely
+ * on the presence of the `infocmp` executable to do the job for us (failing
+ * silently if the program is not available or refused to run).
+ */
+struct escape_sequence_entry {
+	struct hashmap_entry entry;
+	char sequence[FLEX_ARRAY];
+};
+
+static int sequence_entry_cmp(const void *hashmap_cmp_fn_data,
+			      const struct escape_sequence_entry *e1,
+			      const struct escape_sequence_entry *e2,
+			      const void *keydata)
+{
+	return strcmp(e1->sequence, keydata ? keydata : e2->sequence);
+}
+
+static int is_known_escape_sequence(const char *sequence)
+{
+	static struct hashmap sequences;
+	static int initialized;
+
+	if (!initialized) {
+		struct child_process cp = CHILD_PROCESS_INIT;
+		struct strbuf buf = STRBUF_INIT;
+		char *p, *eol;
+
+		hashmap_init(&sequences, (hashmap_cmp_fn)sequence_entry_cmp,
+			     NULL, 0);
+
+		argv_array_pushl(&cp.args, "infocmp", "-L", "-1", NULL);
+		if (pipe_command(&cp, NULL, 0, &buf, 0, NULL, 0))
+			strbuf_setlen(&buf, 0);
+
+		for (eol = p = buf.buf; *p; p = eol + 1) {
+			p = strchr(p, '=');
+			if (!p)
+				break;
+			p++;
+			eol = strchrnul(p, '\n');
+
+			if (starts_with(p, "\\E")) {
+				char *comma = memchr(p, ',', eol - p);
+				struct escape_sequence_entry *e;
+
+				p[0] = '^';
+				p[1] = '[';
+				FLEX_ALLOC_MEM(e, sequence, p, comma - p);
+				hashmap_entry_init(&e->entry,
+						   strhash(e->sequence));
+				hashmap_add(&sequences, &e->entry);
+			}
+			if (!*eol)
+				break;
+		}
+		initialized = 1;
+	}
+
+	return !!hashmap_get_from_hash(&sequences, strhash(sequence), sequence);
+}
+
 int read_key_without_echo(struct strbuf *buf)
 {
 	static int warning_displayed;

@@ -271,7 +337,12 @@ int read_key_without_echo(struct strbuf *buf)
 		 * Start by replacing the Escape byte with ^[ */
 		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
 
-		for (;;) {
+		/*
+		 * Query the terminal capabilities once about all the Escape
+		 * sequences it knows about, so that we can avoid waiting for
+		 * half a second when we know that the sequence is complete.
+		 */
+		while (!is_known_escape_sequence(buf->buf)) {
 			struct pollfd pfd = { .fd = 0, .events = POLLIN };
 
 			if (poll(&pfd, 1, 500) < 1)

-- 
gitgitgadget

[PATCH 4/9] terminal: accommodate Git for Windows' default terminal

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:12

From: Johannes Schindelin <redacted>

Git for Windows' Git Bash runs in MinTTY by default, which does not have
a Win32 Console instance, but uses MSYS2 pseudo terminals instead.

This is a problem, as Git for Windows does not want to use the MSYS2
emulation layer for Git itself, and therefore has no direct way to
interact with that pseudo terminal.

As a workaround, use the `stty` utility (which is included in Git for
Windows, and which *is* an MSYS2 program, so it knows how to deal with
the pseudo terminal).

Note: If Git runs in a regular CMD or PowerShell window, there *is* a
regular Win32 Console to work with. This is not a problem for the MSYS2
`stty`: it copes with this scenario just fine.

Also note that we introduce support for more bits than would be
necessary for a mere `disable_echo()` here, in preparation for the
upcoming `enable_non_canonical()` function.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/compat/terminal.c b/compat/terminal.c
index 1fb40b3a0a..16e9949da1 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -2,6 +2,8 @@
 #include "compat/terminal.h"
 #include "sigchain.h"
 #include "strbuf.h"
+#include "run-command.h"
+#include "string-list.h"
 
 #if defined(HAVE_DEV_TTY) || defined(GIT_WINDOWS_NATIVE)

@@ -64,11 +66,28 @@ static int disable_echo(void)
 #define OUTPUT_PATH "CONOUT$"
 #define FORCE_TEXT "t"
 
+static int use_stty = 1;
+static struct string_list stty_restore = STRING_LIST_INIT_DUP;
 static HANDLE hconin = INVALID_HANDLE_VALUE;
 static DWORD cmode;
 
 static void restore_term(void)
 {
+	if (use_stty) {
+		int i;
+		struct child_process cp = CHILD_PROCESS_INIT;
+
+		if (stty_restore.nr == 0)
+			return;
+
+		argv_array_push(&cp.args, "stty");
+		for (i = 0; i < stty_restore.nr; i++)
+			argv_array_push(&cp.args, stty_restore.items[i].string);
+		run_command(&cp);
+		string_list_clear(&stty_restore, 0);
+		return;
+	}
+
 	if (hconin == INVALID_HANDLE_VALUE)
 		return;

@@ -79,6 +98,37 @@ static void restore_term(void)
 
 static int disable_bits(DWORD bits)
 {
+	if (use_stty) {
+		struct child_process cp = CHILD_PROCESS_INIT;
+
+		argv_array_push(&cp.args, "stty");
+
+		if (bits & ENABLE_LINE_INPUT) {
+			string_list_append(&stty_restore, "icanon");
+			argv_array_push(&cp.args, "-icanon");
+		}
+
+		if (bits & ENABLE_ECHO_INPUT) {
+			string_list_append(&stty_restore, "echo");
+			argv_array_push(&cp.args, "-echo");
+		}
+
+		if (bits & ENABLE_PROCESSED_INPUT) {
+			string_list_append(&stty_restore, "-ignbrk");
+			string_list_append(&stty_restore, "intr");
+			string_list_append(&stty_restore, "^c");
+			argv_array_push(&cp.args, "ignbrk");
+			argv_array_push(&cp.args, "intr");
+			argv_array_push(&cp.args, "");
+		}
+
+		if (run_command(&cp) == 0)
+			return 0;
+
+		/* `stty` could not be executed; access the Console directly */
+		use_stty = 0;
+	}
+
 	hconin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
 	    FILE_SHARE_READ, NULL, OPEN_EXISTING,
 	    FILE_ATTRIBUTE_NORMAL, NULL);

-- 
gitgitgadget

[PATCH 3/9] terminal: make the code of disable_echo() reusable

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:13

From: Johannes Schindelin <redacted>

We are about to introduce the function `enable_non_canonical()`, which
shares almost the complete code with `disable_echo()`.

Let's prepare for that, by refactoring out that shared code.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index fa13ee672d..1fb40b3a0a 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -32,7 +32,7 @@ static void restore_term(void)
 	term_fd = -1;
 }
 
-static int disable_echo(void)
+static int disable_bits(tcflag_t bits)
 {
 	struct termios t;

@@ -43,7 +43,7 @@ static int disable_echo(void)
 	old_term = t;
 	sigchain_push_common(restore_term_on_signal);
 
-	t.c_lflag &= ~ECHO;
+	t.c_lflag &= ~bits;
 	if (!tcsetattr(term_fd, TCSAFLUSH, &t))
 		return 0;

@@ -53,6 +53,11 @@ static int disable_echo(void)
 	return -1;
 }
 
+static int disable_echo(void)
+{
+	return disable_bits(ECHO);
+}
+
 #elif defined(GIT_WINDOWS_NATIVE)
 
 #define INPUT_PATH "CONIN$"

@@ -72,7 +77,7 @@ static void restore_term(void)
 	hconin = INVALID_HANDLE_VALUE;
 }
 
-static int disable_echo(void)
+static int disable_bits(DWORD bits)
 {
 	hconin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
 	    FILE_SHARE_READ, NULL, OPEN_EXISTING,

@@ -82,7 +87,7 @@ static int disable_echo(void)
 
 	GetConsoleMode(hconin, &cmode);
 	sigchain_push_common(restore_term_on_signal);
-	if (!SetConsoleMode(hconin, cmode & (~ENABLE_ECHO_INPUT))) {
+	if (!SetConsoleMode(hconin, cmode & ~bits)) {
 		CloseHandle(hconin);
 		hconin = INVALID_HANDLE_VALUE;
 		return -1;

@@ -91,6 +96,12 @@ static int disable_echo(void)
 	return 0;
 }
 
+static int disable_echo(void)
+{
+	return disable_bits(ENABLE_ECHO_INPUT);
+}
+
+
 #endif
 
 #ifndef FORCE_TEXT

-- 
gitgitgadget

[PATCH 7/9] built-in add -p: handle Escape sequences in interactive.singlekey mode

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:14

From: Johannes Schindelin <redacted>

This recapitulates part of b5cc003253c8 (add -i: ignore terminal escape
sequences, 2011-05-17):

    add -i: ignore terminal escape sequences

    On the author's terminal, the up-arrow input sequence is ^[[A, and
    thus fat-fingering an up-arrow into 'git checkout -p' is quite
    dangerous: git-add--interactive.perl will ignore the ^[ and [
    characters and happily treat A as "discard everything".

    As a band-aid fix, use Term::Cap to get all terminal capabilities.
    Then use the heuristic that any capability value that starts with ^[
    (i.e., \e in perl) must be a key input sequence.  Finally, given an
    input that starts with ^[, read more characters until we have read a
    full escape sequence, then return that to the caller.  We use a
    timeout of 0.5 seconds on the subsequent reads to avoid getting stuck
    if the user actually input a lone ^[.

    Since none of the currently recognized keys start with ^[, the net
    result is that the sequence as a whole will be ignored and the help
    displayed.

Note that we leave part for later which uses "Term::Cap to get all
terminal capabilities", for several reasons:

1. it is actually not really necessary, as the timeout of 0.5 seconds
   should be plenty sufficient to catch Escape sequences,

2. it is cleaner to keep the change to special-case Escape sequences
   separate from the change that reads all terminal capabilities to
   speed things up, and

3. in practice, relying on the terminal capabilities is a bit overrated,
   as the information could be incomplete, or plain wrong. For example,
   in this developer's tmux sessions, the terminal capabilities claim
   that the "cursor up" sequence is ^[M, but the actual sequence
   produced by the "cursor up" key is ^[[A.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index 1b2564042a..b7f58d1781 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -161,6 +161,37 @@ static int enable_non_canonical(void)
 	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
 }
 
+/*
+ * Override `getchar()`, as the default implementation does not use
+ * `ReadFile()`.
+ *
+ * This poses a problem when we want to see whether the standard
+ * input has more characters, as the default of Git for Windows is to start the
+ * Bash in a MinTTY, which uses a named pipe to emulate a pty, in which case
+ * our `poll()` emulation calls `PeekNamedPipe()`, which seems to require
+ * `ReadFile()` to be called first to work properly (it only reports 0
+ * available bytes, otherwise).
+ *
+ * So let's just override `getchar()` with a version backed by `ReadFile()` and
+ * go our merry ways from here.
+ */
+static int mingw_getchar(void)
+{
+	DWORD read = 0;
+	unsigned char ch;
+
+	if (!ReadFile(GetStdHandle(STD_INPUT_HANDLE), &ch, 1, &read, NULL))
+		return EOF;
+
+	if (!read) {
+		error("Unexpected 0 read");
+		return EOF;
+	}
+
+	return ch;
+}
+#define getchar mingw_getchar
+
 #endif
 
 #ifndef FORCE_TEXT

@@ -228,8 +259,31 @@ int read_key_without_echo(struct strbuf *buf)
 		restore_term();
 		return EOF;
 	}
-
 	strbuf_addch(buf, ch);
+
+	if (ch == '\033' /* ESC */) {
+		/*
+		 * We are most likely looking at an Escape sequence. Let's try
+		 * to read more bytes, waiting at most half a second, assuming
+		 * that the sequence is complete if we did not receive any byte
+		 * within that time.
+		 *
+		 * Start by replacing the Escape byte with ^[ */
+		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
+
+		for (;;) {
+			struct pollfd pfd = { .fd = 0, .events = POLLIN };
+
+			if (poll(&pfd, 1, 500) < 1)
+				break;
+
+			ch = getchar();
+			if (ch == EOF)
+				return 0;
+			strbuf_addch(buf, ch);
+		}
+	}
+
 	restore_term();
 	return 0;
 }

-- 
gitgitgadget

[PATCH 5/9] terminal: add a new function to read a single keystroke

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:14

From: Johannes Schindelin <redacted>

Typically, input on the command-line is line-based. It is actually not
really easy to get single characters (or better put: keystrokes).

We provide two implementations here:

- One that handles `/dev/tty` based systems as well as native Windows.
  The former uses the `tcsetattr()` function to put the terminal into
  "raw mode", which allows us to read individual keystrokes, one by one.
  The latter uses `stty.exe` to do the same, falling back to direct
  Win32 Console access.

  Thanks to the refactoring leading up to this commit, this is a single
  function, with the platform-specific details hidden away in
  conditionally-compiled code blocks.

- A fall-back which simply punts and reads back an entire line.

Note that the function writes the keystroke into an `strbuf` rather than
a `char`, in preparation for reading Escape sequences (e.g. when the
user hit an arrow key). This is also required for UTF-8 sequences in
case the keystroke corresponds to a non-ASCII letter.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++
 compat/terminal.h |  3 +++
 2 files changed, 58 insertions(+)

diff --git a/compat/terminal.c b/compat/terminal.c
index 16e9949da1..1b2564042a 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -60,6 +60,11 @@ static int disable_echo(void)
 	return disable_bits(ECHO);
 }
 
+static int enable_non_canonical(void)
+{
+	return disable_bits(ICANON | ECHO);
+}
+
 #elif defined(GIT_WINDOWS_NATIVE)
 
 #define INPUT_PATH "CONIN$"

@@ -151,6 +156,10 @@ static int disable_echo(void)
 	return disable_bits(ENABLE_ECHO_INPUT);
 }
 
+static int enable_non_canonical(void)
+{
+	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
+}
 
 #endif

@@ -198,6 +207,33 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+int read_key_without_echo(struct strbuf *buf)
+{
+	static int warning_displayed;
+	int ch;
+
+	if (warning_displayed || enable_non_canonical() < 0) {
+		if (!warning_displayed) {
+			warning("reading single keystrokes not supported on "
+				"this platform; reading line instead");
+			warning_displayed = 1;
+		}
+
+		return strbuf_getline(buf, stdin);
+	}
+
+	strbuf_reset(buf);
+	ch = getchar();
+	if (ch == EOF) {
+		restore_term();
+		return EOF;
+	}
+
+	strbuf_addch(buf, ch);
+	restore_term();
+	return 0;
+}
+
 #else
 
 char *git_terminal_prompt(const char *prompt, int echo)

@@ -205,4 +241,23 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return getpass(prompt);
 }
 
+int read_key_without_echo(struct strbuf *buf)
+{
+	static int warning_displayed;
+	const char *res;
+
+	if (!warning_displayed) {
+		warning("reading single keystrokes not supported on this "
+			"platform; reading line instead");
+		warning_displayed = 1;
+	}
+
+	res = getpass("");
+	strbuf_reset(buf);
+	if (!res)
+		return EOF;
+	strbuf_addstr(buf, res);
+	return 0;
+}
+
 #endif

diff --git a/compat/terminal.h b/compat/terminal.h
index 97db7cd69d..a9d52b8464 100644
--- a/compat/terminal.h
+++ b/compat/terminal.h

@@ -3,4 +3,7 @@
 
 char *git_terminal_prompt(const char *prompt, int echo);
 
+/* Read a single keystroke, without echoing it to the terminal */
+int read_key_without_echo(struct strbuf *buf);
+
 #endif /* COMPAT_TERMINAL_H */

-- 
gitgitgadget

[PATCH 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-21 22:42:17

From: Johannes Schindelin <redacted>

This job runs the test suite twice, once in regular mode, and once with
a whole slew of `GIT_TEST_*` variables set.

Now that the built-in version of `git add --interactive` is
feature-complete, let's also throw `GIT_TEST_MULTI_PACK_INDEX` into that
fray.

Signed-off-by: Johannes Schindelin <redacted>
---
 ci/run-build-and-tests.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index ff0ef7f08e..4df54c4efe 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh

@@ -20,6 +20,7 @@ linux-gcc)
 	export GIT_TEST_OE_DELTA_SIZE=5
 	export GIT_TEST_COMMIT_GRAPH=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
+	export GIT_TEST_ADD_I_USE_BUILTIN=1
 	make test
 	;;
 linux-gcc-4.8)

-- 
gitgitgadget

Re: [PATCH 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job

From: SZEDER Gábor <hidden>
Date: 2019-12-21 22:54:11

On Sat, Dec 21, 2019 at 10:42:00PM +0000, Johannes Schindelin via GitGitGadget wrote:

From: Johannes Schindelin <redacted>

This job runs the test suite twice, once in regular mode, and once with
a whole slew of `GIT_TEST_*` variables set.

Now that the built-in version of `git add --interactive` is
feature-complete, let's also throw `GIT_TEST_MULTI_PACK_INDEX` into that

GIT_TEST_MULTI_PACK_INDEX? ;)

quoted hunk

fray.

Signed-off-by: Johannes Schindelin <redacted>
---
 ci/run-build-and-tests.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index ff0ef7f08e..4df54c4efe 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh

@@ -20,6 +20,7 @@ linux-gcc)
 	export GIT_TEST_OE_DELTA_SIZE=5
 	export GIT_TEST_COMMIT_GRAPH=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
+	export GIT_TEST_ADD_I_USE_BUILTIN=1
 	make test
 	;;
 linux-gcc-4.8)

-- 
gitgitgadget

Re: [PATCH 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job

From: Johannes Schindelin <hidden>
Date: 2019-12-25 11:56:38

Hi Gábor,

On Sat, 21 Dec 2019, SZEDER Gábor wrote:

On Sat, Dec 21, 2019 at 10:42:00PM +0000, Johannes Schindelin via GitGitGadget wrote:

quoted

From: Johannes Schindelin <redacted>

This job runs the test suite twice, once in regular mode, and once with
a whole slew of `GIT_TEST_*` variables set.

Now that the built-in version of `git add --interactive` is
feature-complete, let's also throw `GIT_TEST_MULTI_PACK_INDEX` into that

GIT_TEST_MULTI_PACK_INDEX? ;)

Whoops. Copy/paste fail.

Fixed in v2,
Dscho

quoted

fray.

Signed-off-by: Johannes Schindelin <redacted>
---
 ci/run-build-and-tests.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index ff0ef7f08e..4df54c4efe 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh

@@ -20,6 +20,7 @@ linux-gcc)
 	export GIT_TEST_OE_DELTA_SIZE=5
 	export GIT_TEST_COMMIT_GRAPH=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
+	export GIT_TEST_ADD_I_USE_BUILTIN=1
 	make test
 	;;
 linux-gcc-4.8)
--

gitgitgadget

[PATCH v2 0/9] built-in add -p: add support for the same config settings as the Perl version

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:06

This is the final leg of the journey to a fully built-in git add: the git
add -i and git add -p modes were re-implemented in C, but they lacked
support for a couple of config settings.

The one that sticks out most is the interactive.singleKey setting: it was
particularly hard to get to work, especially on Windows.

It also seems to be the setting that is incomplete already in the Perl
version of the interactive add command: while the name of the config setting
suggests that it applies to all of the interactive add, including the main
loop of git add --interactive and to the file selections in that command, it
does not. Only the git add --patch mode respects that setting.

As it is outside the purpose of the conversion of git-add--interactive.perl 
to C, we will leave that loose end for some future date.

Changes since v1:

 * Fixed the commit message where a copy/paste fail made it talk about
   another GIT_TEST_* variable than the GIT_TEST_ADD_I_USE_BUILTIN one.

Johannes Schindelin (9):
  built-in add -p: support interactive.diffFilter
  built-in add -p: handle diff.algorithm
  terminal: make the code of disable_echo() reusable
  terminal: accommodate Git for Windows' default terminal
  terminal: add a new function to read a single keystroke
  built-in add -p: respect the `interactive.singlekey` config setting
  built-in add -p: handle Escape sequences in interactive.singlekey mode
  built-in add -p: handle Escape sequences more efficiently
  ci: include the built-in `git add -i` in the `linux-gcc` job

 add-interactive.c         |  19 +++
 add-interactive.h         |   4 +
 add-patch.c               |  57 ++++++++-
 ci/run-build-and-tests.sh |   1 +
 compat/terminal.c         | 249 +++++++++++++++++++++++++++++++++++++-
 compat/terminal.h         |   3 +
 6 files changed, 325 insertions(+), 8 deletions(-)


base-commit: c480eeb574e649a19f27dc09a994e45f9b2c2622
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-175%2Fdscho%2Fadd-p-in-c-config-settings-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-175/dscho/add-p-in-c-config-settings-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/175

Range-diff vs v1:

  1:  a7355776d6 =  1:  f45ff08bd0 built-in add -p: support interactive.diffFilter
  2:  74958419f6 !  2:  e9c4a13cbf built-in add -p: handle diff.algorithm
     @@ -62,7 +62,7 @@
      @@
       	int res;
       
     - 	argv_array_pushv(&args, s->mode->diff);
     + 	argv_array_pushv(&args, s->mode->diff_cmd);
      +	if (diff_algorithm)
      +		argv_array_pushf(&args, "--diff-algorithm=%s", diff_algorithm);
       	if (s->revision) {
  3:  7631c1ea8c =  3:  e643554dba terminal: make the code of disable_echo() reusable
  4:  a77fa914da =  4:  bd2306c5d5 terminal: accommodate Git for Windows' default terminal
  5:  3996d7997a =  5:  190fb4f5e9 terminal: add a new function to read a single keystroke
  6:  6d6794089d !  6:  167dfa37dd built-in add -p: respect the `interactive.singlekey` config setting
     @@ -54,7 +54,7 @@
      +#include "compat/terminal.h"
       
       enum prompt_mode_type {
     - 	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK
     + 	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK,
      @@
       	return 0;
       }
  7:  fd5a129776 =  7:  32067bebe8 built-in add -p: handle Escape sequences in interactive.singlekey mode
  8:  af9b598738 =  8:  703719ffce built-in add -p: handle Escape sequences more efficiently
  9:  9719604a1f !  9:  23a3a47b01 ci: include the built-in `git add -i` in the `linux-gcc` job
     @@ -6,8 +6,8 @@
          a whole slew of `GIT_TEST_*` variables set.
      
          Now that the built-in version of `git add --interactive` is
     -    feature-complete, let's also throw `GIT_TEST_MULTI_PACK_INDEX` into that
     -    fray.
     +    feature-complete, let's also throw `GIT_TEST_ADD_I_USE_BUILTIN` into
     +    that fray.
      
          Signed-off-by: Johannes Schindelin [off-list ref]
      

-- 
gitgitgadget

[PATCH v2 1/9] built-in add -p: support interactive.diffFilter

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:07

From: Johannes Schindelin <redacted>

The Perl version supports post-processing the colored diff (that is
generated in addition to the uncolored diff, intended to offer a
prettier user experience) by a command configured via that config
setting, and now the built-in version does that, too.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 12 ++++++++++++
 add-interactive.h |  3 +++
 add-patch.c       | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index a5bb14f2f4..1786ea29c4 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -52,6 +52,17 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 		diff_get_color(s->use_color, DIFF_FILE_OLD));
 	init_color(r, s, "new", s->file_new_color,
 		diff_get_color(s->use_color, DIFF_FILE_NEW));
+
+	FREE_AND_NULL(s->interactive_diff_filter);
+	git_config_get_string("interactive.difffilter",
+			      &s->interactive_diff_filter);
+}
+
+void clear_add_i_state(struct add_i_state *s)
+{
+	FREE_AND_NULL(s->interactive_diff_filter);
+	memset(s, 0, sizeof(*s));
+	s->use_color = -1;
 }
 
 /*

@@ -1149,6 +1160,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	strbuf_release(&print_file_item_data.worktree);
 	strbuf_release(&header);
 	prefix_item_list_clear(&commands);
+	clear_add_i_state(&s);
 
 	return res;
 }

diff --git a/add-interactive.h b/add-interactive.h
index b2f23479c5..46c73867ad 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -15,9 +15,12 @@ struct add_i_state {
 	char context_color[COLOR_MAXLEN];
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
+
+	char *interactive_diff_filter;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);
+void clear_add_i_state(struct add_i_state *s);
 
 struct repository;
 struct pathspec;

diff --git a/add-patch.c b/add-patch.c
index 46c6c183d5..78bde41df0 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -398,6 +398,7 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 
 	if (want_color_fd(1, -1)) {
 		struct child_process colored_cp = CHILD_PROCESS_INIT;
+		const char *diff_filter = s->s.interactive_diff_filter;
 
 		setup_child_process(s, &colored_cp, NULL);
 		xsnprintf((char *)args.argv[color_arg_index], 8, "--color");

@@ -407,6 +408,24 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		argv_array_clear(&args);
 		if (res)
 			return error(_("could not parse colored diff"));
+
+		if (diff_filter) {
+			struct child_process filter_cp = CHILD_PROCESS_INIT;
+
+			setup_child_process(s, &filter_cp,
+					    diff_filter, NULL);
+			filter_cp.git_cmd = 0;
+			filter_cp.use_shell = 1;
+			strbuf_reset(&s->buf);
+			if (pipe_command(&filter_cp,
+					 colored->buf, colored->len,
+					 &s->buf, colored->len,
+					 NULL, 0) < 0)
+				return error(_("failed to run '%s'"),
+					     diff_filter);
+			strbuf_swap(colored, &s->buf);
+		}
+
 		strbuf_complete_line(colored);
 		colored_p = colored->buf;
 		colored_pend = colored_p + colored->len;

@@ -531,6 +550,9 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 						   colored_pend - colored_p);
 			if (colored_eol)
 				colored_p = colored_eol + 1;
+			else if (p != pend)
+				/* colored shorter than non-colored? */
+				goto mismatched_output;
 			else
 				colored_p = colored_pend;

@@ -555,6 +577,15 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		 */
 		hunk->splittable_into++;
 
+	/* non-colored shorter than colored? */
+	if (colored_p != colored_pend) {
+mismatched_output:
+		error(_("mismatched output from interactive.diffFilter"));
+		advise(_("Your filter must maintain a one-to-one correspondence\n"
+			 "between its input and output lines."));
+		return -1;
+	}
+
 	return 0;
 }

@@ -1612,6 +1643,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	    parse_diff(&s, ps) < 0) {
 		strbuf_release(&s.plain);
 		strbuf_release(&s.colored);
+		clear_add_i_state(&s.s);
 		return -1;
 	}

@@ -1630,5 +1662,6 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	strbuf_release(&s.buf);
 	strbuf_release(&s.plain);
 	strbuf_release(&s.colored);
+	clear_add_i_state(&s.s);
 	return 0;
 }

-- 
gitgitgadget

[PATCH v2 2/9] built-in add -p: handle diff.algorithm

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:07

From: Johannes Schindelin <redacted>

The Perl version of `git add -p` reads the config setting
`diff.algorithm` and if set, uses it to generate the diff using the
specified algorithm.

This patch ports that functionality to the C version.

Note: just like `git-add--interactive.perl`, we do _not_ respect this
config setting in `git add -i`'s `diff` command, but _only_ in the
`patch` command.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 5 +++++
 add-interactive.h | 2 +-
 add-patch.c       | 3 +++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/add-interactive.c b/add-interactive.c
index 1786ea29c4..9e4bcb382c 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -56,11 +56,16 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	FREE_AND_NULL(s->interactive_diff_filter);
 	git_config_get_string("interactive.difffilter",
 			      &s->interactive_diff_filter);
+
+	FREE_AND_NULL(s->interactive_diff_algorithm);
+	git_config_get_string("diff.algorithm",
+			      &s->interactive_diff_algorithm);
 }
 
 void clear_add_i_state(struct add_i_state *s)
 {
 	FREE_AND_NULL(s->interactive_diff_filter);
+	FREE_AND_NULL(s->interactive_diff_algorithm);
 	memset(s, 0, sizeof(*s));
 	s->use_color = -1;
 }

diff --git a/add-interactive.h b/add-interactive.h
index 46c73867ad..923efaf527 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -16,7 +16,7 @@ struct add_i_state {
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
 
-	char *interactive_diff_filter;
+	char *interactive_diff_filter, *interactive_diff_algorithm;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);

diff --git a/add-patch.c b/add-patch.c
index 78bde41df0..8f2ee8688b 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -360,6 +360,7 @@ static int is_octal(const char *p, size_t len)
 static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 {
 	struct argv_array args = ARGV_ARRAY_INIT;
+	const char *diff_algorithm = s->s.interactive_diff_algorithm;
 	struct strbuf *plain = &s->plain, *colored = NULL;
 	struct child_process cp = CHILD_PROCESS_INIT;
 	char *p, *pend, *colored_p = NULL, *colored_pend = NULL, marker = '\0';

@@ -369,6 +370,8 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 	int res;
 
 	argv_array_pushv(&args, s->mode->diff_cmd);
+	if (diff_algorithm)
+		argv_array_pushf(&args, "--diff-algorithm=%s", diff_algorithm);
 	if (s->revision) {
 		struct object_id oid;
 		argv_array_push(&args,

-- 
gitgitgadget

[PATCH v2 3/9] terminal: make the code of disable_echo() reusable

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:10

From: Johannes Schindelin <redacted>

We are about to introduce the function `enable_non_canonical()`, which
shares almost the complete code with `disable_echo()`.

Let's prepare for that, by refactoring out that shared code.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index fa13ee672d..1fb40b3a0a 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -32,7 +32,7 @@ static void restore_term(void)
 	term_fd = -1;
 }
 
-static int disable_echo(void)
+static int disable_bits(tcflag_t bits)
 {
 	struct termios t;

@@ -43,7 +43,7 @@ static int disable_echo(void)
 	old_term = t;
 	sigchain_push_common(restore_term_on_signal);
 
-	t.c_lflag &= ~ECHO;
+	t.c_lflag &= ~bits;
 	if (!tcsetattr(term_fd, TCSAFLUSH, &t))
 		return 0;

@@ -53,6 +53,11 @@ static int disable_echo(void)
 	return -1;
 }
 
+static int disable_echo(void)
+{
+	return disable_bits(ECHO);
+}
+
 #elif defined(GIT_WINDOWS_NATIVE)
 
 #define INPUT_PATH "CONIN$"

@@ -72,7 +77,7 @@ static void restore_term(void)
 	hconin = INVALID_HANDLE_VALUE;
 }
 
-static int disable_echo(void)
+static int disable_bits(DWORD bits)
 {
 	hconin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
 	    FILE_SHARE_READ, NULL, OPEN_EXISTING,

@@ -82,7 +87,7 @@ static int disable_echo(void)
 
 	GetConsoleMode(hconin, &cmode);
 	sigchain_push_common(restore_term_on_signal);
-	if (!SetConsoleMode(hconin, cmode & (~ENABLE_ECHO_INPUT))) {
+	if (!SetConsoleMode(hconin, cmode & ~bits)) {
 		CloseHandle(hconin);
 		hconin = INVALID_HANDLE_VALUE;
 		return -1;

@@ -91,6 +96,12 @@ static int disable_echo(void)
 	return 0;
 }
 
+static int disable_echo(void)
+{
+	return disable_bits(ENABLE_ECHO_INPUT);
+}
+
+
 #endif
 
 #ifndef FORCE_TEXT

-- 
gitgitgadget

[PATCH v2 4/9] terminal: accommodate Git for Windows' default terminal

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:11

From: Johannes Schindelin <redacted>

Git for Windows' Git Bash runs in MinTTY by default, which does not have
a Win32 Console instance, but uses MSYS2 pseudo terminals instead.

This is a problem, as Git for Windows does not want to use the MSYS2
emulation layer for Git itself, and therefore has no direct way to
interact with that pseudo terminal.

As a workaround, use the `stty` utility (which is included in Git for
Windows, and which *is* an MSYS2 program, so it knows how to deal with
the pseudo terminal).

Note: If Git runs in a regular CMD or PowerShell window, there *is* a
regular Win32 Console to work with. This is not a problem for the MSYS2
`stty`: it copes with this scenario just fine.

Also note that we introduce support for more bits than would be
necessary for a mere `disable_echo()` here, in preparation for the
upcoming `enable_non_canonical()` function.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/compat/terminal.c b/compat/terminal.c
index 1fb40b3a0a..16e9949da1 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -2,6 +2,8 @@
 #include "compat/terminal.h"
 #include "sigchain.h"
 #include "strbuf.h"
+#include "run-command.h"
+#include "string-list.h"
 
 #if defined(HAVE_DEV_TTY) || defined(GIT_WINDOWS_NATIVE)

@@ -64,11 +66,28 @@ static int disable_echo(void)
 #define OUTPUT_PATH "CONOUT$"
 #define FORCE_TEXT "t"
 
+static int use_stty = 1;
+static struct string_list stty_restore = STRING_LIST_INIT_DUP;
 static HANDLE hconin = INVALID_HANDLE_VALUE;
 static DWORD cmode;
 
 static void restore_term(void)
 {
+	if (use_stty) {
+		int i;
+		struct child_process cp = CHILD_PROCESS_INIT;
+
+		if (stty_restore.nr == 0)
+			return;
+
+		argv_array_push(&cp.args, "stty");
+		for (i = 0; i < stty_restore.nr; i++)
+			argv_array_push(&cp.args, stty_restore.items[i].string);
+		run_command(&cp);
+		string_list_clear(&stty_restore, 0);
+		return;
+	}
+
 	if (hconin == INVALID_HANDLE_VALUE)
 		return;

@@ -79,6 +98,37 @@ static void restore_term(void)
 
 static int disable_bits(DWORD bits)
 {
+	if (use_stty) {
+		struct child_process cp = CHILD_PROCESS_INIT;
+
+		argv_array_push(&cp.args, "stty");
+
+		if (bits & ENABLE_LINE_INPUT) {
+			string_list_append(&stty_restore, "icanon");
+			argv_array_push(&cp.args, "-icanon");
+		}
+
+		if (bits & ENABLE_ECHO_INPUT) {
+			string_list_append(&stty_restore, "echo");
+			argv_array_push(&cp.args, "-echo");
+		}
+
+		if (bits & ENABLE_PROCESSED_INPUT) {
+			string_list_append(&stty_restore, "-ignbrk");
+			string_list_append(&stty_restore, "intr");
+			string_list_append(&stty_restore, "^c");
+			argv_array_push(&cp.args, "ignbrk");
+			argv_array_push(&cp.args, "intr");
+			argv_array_push(&cp.args, "");
+		}
+
+		if (run_command(&cp) == 0)
+			return 0;
+
+		/* `stty` could not be executed; access the Console directly */
+		use_stty = 0;
+	}
+
 	hconin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
 	    FILE_SHARE_READ, NULL, OPEN_EXISTING,
 	    FILE_ATTRIBUTE_NORMAL, NULL);

-- 
gitgitgadget

[PATCH v2 6/9] built-in add -p: respect the `interactive.singlekey` config setting

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:12

From: Johannes Schindelin <redacted>

The Perl version of `git add -p` supports this config setting to allow
users to input commands via single characters (as opposed to having to
press the <Enter> key afterwards).

This is an opt-in feature because it requires Perl packages
(Term::ReadKey and Term::Cap, where it tries to handle an absence of the
latter package gracefully) to work. Note that at least on Ubuntu, that
Perl package is not installed by default (it needs to be installed via
`sudo apt-get install libterm-readkey-perl`), so this feature is
probably not used a whole lot.

In C, we obviously do not have these packages available, but we just
introduced `read_single_keystroke()` that is similar to what
Term::ReadKey provides, and we use that here.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c |  2 ++
 add-interactive.h |  1 +
 add-patch.c       | 21 +++++++++++++++++----
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index 9e4bcb382c..39c3896494 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -60,6 +60,8 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	FREE_AND_NULL(s->interactive_diff_algorithm);
 	git_config_get_string("diff.algorithm",
 			      &s->interactive_diff_algorithm);
+
+	git_config_get_bool("interactive.singlekey", &s->use_single_key);
 }
 
 void clear_add_i_state(struct add_i_state *s)

diff --git a/add-interactive.h b/add-interactive.h
index 923efaf527..693f125e8e 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -16,6 +16,7 @@ struct add_i_state {
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
 
+	int use_single_key;
 	char *interactive_diff_filter, *interactive_diff_algorithm;
 };

diff --git a/add-patch.c b/add-patch.c
index 8f2ee8688b..d8dafa8168 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -6,6 +6,7 @@
 #include "pathspec.h"
 #include "color.h"
 #include "diff.h"
+#include "compat/terminal.h"
 
 enum prompt_mode_type {
 	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK,

@@ -1149,14 +1150,27 @@ static int run_apply_check(struct add_p_state *s,
 	return 0;
 }
 
+static int read_single_character(struct add_p_state *s)
+{
+	if (s->s.use_single_key) {
+		int res = read_key_without_echo(&s->answer);
+		printf("%s\n", res == EOF ? "" : s->answer.buf);
+		return res;
+	}
+
+	if (strbuf_getline(&s->answer, stdin) == EOF)
+		return EOF;
+	strbuf_trim_trailing_newline(&s->answer);
+	return 0;
+}
+
 static int prompt_yesno(struct add_p_state *s, const char *prompt)
 {
 	for (;;) {
 		color_fprintf(stdout, s->s.prompt_color, "%s", _(prompt));
 		fflush(stdout);
-		if (strbuf_getline(&s->answer, stdin) == EOF)
+		if (read_single_character(s) == EOF)
 			return -1;
-		strbuf_trim_trailing_newline(&s->answer);
 		switch (tolower(s->answer.buf[0])) {
 		case 'n': return 0;
 		case 'y': return 1;

@@ -1396,9 +1410,8 @@ static int patch_update_file(struct add_p_state *s,
 			      _(s->mode->prompt_mode[prompt_mode_type]),
 			      s->buf.buf);
 		fflush(stdout);
-		if (strbuf_getline(&s->answer, stdin) == EOF)
+		if (read_single_character(s) == EOF)
 			break;
-		strbuf_trim_trailing_newline(&s->answer);
 
 		if (!s->answer.len)
 			continue;

-- 
gitgitgadget

[PATCH v2 8/9] built-in add -p: handle Escape sequences more efficiently

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:12

From: Johannes Schindelin <redacted>

When `interactive.singlekey = true`, we react immediately to keystrokes,
even to Escape sequences (e.g. when pressing a cursor key).

The problem with Escape sequences is that we do not really know when
they are done, and as a heuristic we poll standard input for half a
second to make sure that we got all of it.

While waiting half a second is not asking for a whole lot, it can become
quite annoying over time, therefore with this patch, we read the
terminal capabilities (if available) and extract known Escape sequences
from there, then stop polling immediately when we detected that the user
pressed a key that generated such a known sequence.

This recapitulates the remaining part of b5cc003253c8 (add -i: ignore
terminal escape sequences, 2011-05-17).

Note: We do *not* query the terminal capabilities directly. That would
either require a lot of platform-specific code, or it would require
linking to a library such as ncurses.

Linking to a library in the built-ins is something we try very hard to
avoid (we even kicked the libcurl dependency to a non-built-in remote
helper, just to shave off a tiny fraction of a second from Git's startup
time). And the platform-specific code would be a maintenance nightmare.

Even worse: in Git for Windows' case, we would need to query MSYS2
pseudo terminals, which `git.exe` simply cannot do (because it is
intentionally *not* an MSYS2 program).

To address this, we simply spawn `infocmp -L -1` and parse its output
(which works even in Git for Windows, because that helper is included in
the end-user facing installations).

This is done only once, as in the Perl version, but it is done only when
the first Escape sequence is encountered, not upon startup of `git add
-i`; This saves on startup time, yet makes reacting to the first Escape
sequence slightly more sluggish. But it allows us to keep the
terminal-related code encapsulated in the `compat/terminal.c` file.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index b7f58d1781..35bca03d14 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -4,6 +4,7 @@
 #include "strbuf.h"
 #include "run-command.h"
 #include "string-list.h"
+#include "hashmap.h"
 
 #if defined(HAVE_DEV_TTY) || defined(GIT_WINDOWS_NATIVE)

@@ -238,6 +239,71 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+/*
+ * The `is_known_escape_sequence()` function returns 1 if the passed string
+ * corresponds to an Escape sequence that the terminal capabilities contains.
+ *
+ * To avoid depending on ncurses or other platform-specific libraries, we rely
+ * on the presence of the `infocmp` executable to do the job for us (failing
+ * silently if the program is not available or refused to run).
+ */
+struct escape_sequence_entry {
+	struct hashmap_entry entry;
+	char sequence[FLEX_ARRAY];
+};
+
+static int sequence_entry_cmp(const void *hashmap_cmp_fn_data,
+			      const struct escape_sequence_entry *e1,
+			      const struct escape_sequence_entry *e2,
+			      const void *keydata)
+{
+	return strcmp(e1->sequence, keydata ? keydata : e2->sequence);
+}
+
+static int is_known_escape_sequence(const char *sequence)
+{
+	static struct hashmap sequences;
+	static int initialized;
+
+	if (!initialized) {
+		struct child_process cp = CHILD_PROCESS_INIT;
+		struct strbuf buf = STRBUF_INIT;
+		char *p, *eol;
+
+		hashmap_init(&sequences, (hashmap_cmp_fn)sequence_entry_cmp,
+			     NULL, 0);
+
+		argv_array_pushl(&cp.args, "infocmp", "-L", "-1", NULL);
+		if (pipe_command(&cp, NULL, 0, &buf, 0, NULL, 0))
+			strbuf_setlen(&buf, 0);
+
+		for (eol = p = buf.buf; *p; p = eol + 1) {
+			p = strchr(p, '=');
+			if (!p)
+				break;
+			p++;
+			eol = strchrnul(p, '\n');
+
+			if (starts_with(p, "\\E")) {
+				char *comma = memchr(p, ',', eol - p);
+				struct escape_sequence_entry *e;
+
+				p[0] = '^';
+				p[1] = '[';
+				FLEX_ALLOC_MEM(e, sequence, p, comma - p);
+				hashmap_entry_init(&e->entry,
+						   strhash(e->sequence));
+				hashmap_add(&sequences, &e->entry);
+			}
+			if (!*eol)
+				break;
+		}
+		initialized = 1;
+	}
+
+	return !!hashmap_get_from_hash(&sequences, strhash(sequence), sequence);
+}
+
 int read_key_without_echo(struct strbuf *buf)
 {
 	static int warning_displayed;

@@ -271,7 +337,12 @@ int read_key_without_echo(struct strbuf *buf)
 		 * Start by replacing the Escape byte with ^[ */
 		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
 
-		for (;;) {
+		/*
+		 * Query the terminal capabilities once about all the Escape
+		 * sequences it knows about, so that we can avoid waiting for
+		 * half a second when we know that the sequence is complete.
+		 */
+		while (!is_known_escape_sequence(buf->buf)) {
 			struct pollfd pfd = { .fd = 0, .events = POLLIN };
 
 			if (poll(&pfd, 1, 500) < 1)

-- 
gitgitgadget

[PATCH v2 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:14

From: Johannes Schindelin <redacted>

This job runs the test suite twice, once in regular mode, and once with
a whole slew of `GIT_TEST_*` variables set.

Now that the built-in version of `git add --interactive` is
feature-complete, let's also throw `GIT_TEST_ADD_I_USE_BUILTIN` into
that fray.

Signed-off-by: Johannes Schindelin <redacted>
---
 ci/run-build-and-tests.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index ff0ef7f08e..4df54c4efe 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh

@@ -20,6 +20,7 @@ linux-gcc)
 	export GIT_TEST_OE_DELTA_SIZE=5
 	export GIT_TEST_COMMIT_GRAPH=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
+	export GIT_TEST_ADD_I_USE_BUILTIN=1
 	make test
 	;;
 linux-gcc-4.8)

-- 
gitgitgadget

[PATCH v2 7/9] built-in add -p: handle Escape sequences in interactive.singlekey mode

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:16

From: Johannes Schindelin <redacted>

This recapitulates part of b5cc003253c8 (add -i: ignore terminal escape
sequences, 2011-05-17):

    add -i: ignore terminal escape sequences

    On the author's terminal, the up-arrow input sequence is ^[[A, and
    thus fat-fingering an up-arrow into 'git checkout -p' is quite
    dangerous: git-add--interactive.perl will ignore the ^[ and [
    characters and happily treat A as "discard everything".

    As a band-aid fix, use Term::Cap to get all terminal capabilities.
    Then use the heuristic that any capability value that starts with ^[
    (i.e., \e in perl) must be a key input sequence.  Finally, given an
    input that starts with ^[, read more characters until we have read a
    full escape sequence, then return that to the caller.  We use a
    timeout of 0.5 seconds on the subsequent reads to avoid getting stuck
    if the user actually input a lone ^[.

    Since none of the currently recognized keys start with ^[, the net
    result is that the sequence as a whole will be ignored and the help
    displayed.

Note that we leave part for later which uses "Term::Cap to get all
terminal capabilities", for several reasons:

1. it is actually not really necessary, as the timeout of 0.5 seconds
   should be plenty sufficient to catch Escape sequences,

2. it is cleaner to keep the change to special-case Escape sequences
   separate from the change that reads all terminal capabilities to
   speed things up, and

3. in practice, relying on the terminal capabilities is a bit overrated,
   as the information could be incomplete, or plain wrong. For example,
   in this developer's tmux sessions, the terminal capabilities claim
   that the "cursor up" sequence is ^[M, but the actual sequence
   produced by the "cursor up" key is ^[[A.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index 1b2564042a..b7f58d1781 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -161,6 +161,37 @@ static int enable_non_canonical(void)
 	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
 }
 
+/*
+ * Override `getchar()`, as the default implementation does not use
+ * `ReadFile()`.
+ *
+ * This poses a problem when we want to see whether the standard
+ * input has more characters, as the default of Git for Windows is to start the
+ * Bash in a MinTTY, which uses a named pipe to emulate a pty, in which case
+ * our `poll()` emulation calls `PeekNamedPipe()`, which seems to require
+ * `ReadFile()` to be called first to work properly (it only reports 0
+ * available bytes, otherwise).
+ *
+ * So let's just override `getchar()` with a version backed by `ReadFile()` and
+ * go our merry ways from here.
+ */
+static int mingw_getchar(void)
+{
+	DWORD read = 0;
+	unsigned char ch;
+
+	if (!ReadFile(GetStdHandle(STD_INPUT_HANDLE), &ch, 1, &read, NULL))
+		return EOF;
+
+	if (!read) {
+		error("Unexpected 0 read");
+		return EOF;
+	}
+
+	return ch;
+}
+#define getchar mingw_getchar
+
 #endif
 
 #ifndef FORCE_TEXT

@@ -228,8 +259,31 @@ int read_key_without_echo(struct strbuf *buf)
 		restore_term();
 		return EOF;
 	}
-
 	strbuf_addch(buf, ch);
+
+	if (ch == '\033' /* ESC */) {
+		/*
+		 * We are most likely looking at an Escape sequence. Let's try
+		 * to read more bytes, waiting at most half a second, assuming
+		 * that the sequence is complete if we did not receive any byte
+		 * within that time.
+		 *
+		 * Start by replacing the Escape byte with ^[ */
+		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
+
+		for (;;) {
+			struct pollfd pfd = { .fd = 0, .events = POLLIN };
+
+			if (poll(&pfd, 1, 500) < 1)
+				break;
+
+			ch = getchar();
+			if (ch == EOF)
+				return 0;
+			strbuf_addch(buf, ch);
+		}
+	}
+
 	restore_term();
 	return 0;
 }

-- 
gitgitgadget

[PATCH v2 5/9] terminal: add a new function to read a single keystroke

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:17

From: Johannes Schindelin <redacted>

Typically, input on the command-line is line-based. It is actually not
really easy to get single characters (or better put: keystrokes).

We provide two implementations here:

- One that handles `/dev/tty` based systems as well as native Windows.
  The former uses the `tcsetattr()` function to put the terminal into
  "raw mode", which allows us to read individual keystrokes, one by one.
  The latter uses `stty.exe` to do the same, falling back to direct
  Win32 Console access.

  Thanks to the refactoring leading up to this commit, this is a single
  function, with the platform-specific details hidden away in
  conditionally-compiled code blocks.

- A fall-back which simply punts and reads back an entire line.

Note that the function writes the keystroke into an `strbuf` rather than
a `char`, in preparation for reading Escape sequences (e.g. when the
user hit an arrow key). This is also required for UTF-8 sequences in
case the keystroke corresponds to a non-ASCII letter.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++
 compat/terminal.h |  3 +++
 2 files changed, 58 insertions(+)

diff --git a/compat/terminal.c b/compat/terminal.c
index 16e9949da1..1b2564042a 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -60,6 +60,11 @@ static int disable_echo(void)
 	return disable_bits(ECHO);
 }
 
+static int enable_non_canonical(void)
+{
+	return disable_bits(ICANON | ECHO);
+}
+
 #elif defined(GIT_WINDOWS_NATIVE)
 
 #define INPUT_PATH "CONIN$"

@@ -151,6 +156,10 @@ static int disable_echo(void)
 	return disable_bits(ENABLE_ECHO_INPUT);
 }
 
+static int enable_non_canonical(void)
+{
+	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
+}
 
 #endif

@@ -198,6 +207,33 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+int read_key_without_echo(struct strbuf *buf)
+{
+	static int warning_displayed;
+	int ch;
+
+	if (warning_displayed || enable_non_canonical() < 0) {
+		if (!warning_displayed) {
+			warning("reading single keystrokes not supported on "
+				"this platform; reading line instead");
+			warning_displayed = 1;
+		}
+
+		return strbuf_getline(buf, stdin);
+	}
+
+	strbuf_reset(buf);
+	ch = getchar();
+	if (ch == EOF) {
+		restore_term();
+		return EOF;
+	}
+
+	strbuf_addch(buf, ch);
+	restore_term();
+	return 0;
+}
+
 #else
 
 char *git_terminal_prompt(const char *prompt, int echo)

@@ -205,4 +241,23 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return getpass(prompt);
 }
 
+int read_key_without_echo(struct strbuf *buf)
+{
+	static int warning_displayed;
+	const char *res;
+
+	if (!warning_displayed) {
+		warning("reading single keystrokes not supported on this "
+			"platform; reading line instead");
+		warning_displayed = 1;
+	}
+
+	res = getpass("");
+	strbuf_reset(buf);
+	if (!res)
+		return EOF;
+	strbuf_addstr(buf, res);
+	return 0;
+}
+
 #endif

diff --git a/compat/terminal.h b/compat/terminal.h
index 97db7cd69d..a9d52b8464 100644
--- a/compat/terminal.h
+++ b/compat/terminal.h

@@ -3,4 +3,7 @@
 
 char *git_terminal_prompt(const char *prompt, int echo);
 
+/* Read a single keystroke, without echoing it to the terminal */
+int read_key_without_echo(struct strbuf *buf);
+
 #endif /* COMPAT_TERMINAL_H */

-- 
gitgitgadget

Re: [PATCH v2 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job

From: Derrick Stolee <hidden>
Date: 2019-12-26 20:48:48

On 12/25/2019 6:57 AM, Johannes Schindelin via GitGitGadget wrote:

quoted hunk

From: Johannes Schindelin <redacted>

This job runs the test suite twice, once in regular mode, and once with
a whole slew of `GIT_TEST_*` variables set.

Now that the built-in version of `git add --interactive` is
feature-complete, let's also throw `GIT_TEST_ADD_I_USE_BUILTIN` into
that fray.

Signed-off-by: Johannes Schindelin <redacted>
---
 ci/run-build-and-tests.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index ff0ef7f08e..4df54c4efe 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh

@@ -20,6 +20,7 @@ linux-gcc)
 	export GIT_TEST_OE_DELTA_SIZE=5
 	export GIT_TEST_COMMIT_GRAPH=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
+	export GIT_TEST_ADD_I_USE_BUILTIN=1
 	make test

I see that I need to add this to the test-coverage builds.

Will do.
-Stolee

Re: [PATCH v2 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job

From: Johannes Schindelin <hidden>
Date: 2020-01-01 22:10:55

Hi Stolee,

On Thu, 26 Dec 2019, Derrick Stolee wrote:

On 12/25/2019 6:57 AM, Johannes Schindelin via GitGitGadget wrote:

quoted

From: Johannes Schindelin <redacted>

This job runs the test suite twice, once in regular mode, and once with
a whole slew of `GIT_TEST_*` variables set.

Now that the built-in version of `git add --interactive` is
feature-complete, let's also throw `GIT_TEST_ADD_I_USE_BUILTIN` into
that fray.

Signed-off-by: Johannes Schindelin <redacted>
---
 ci/run-build-and-tests.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index ff0ef7f08e..4df54c4efe 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh

@@ -20,6 +20,7 @@ linux-gcc)
 	export GIT_TEST_OE_DELTA_SIZE=5
 	export GIT_TEST_COMMIT_GRAPH=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
+	export GIT_TEST_ADD_I_USE_BUILTIN=1
 	make test

I see that I need to add this to the test-coverage builds.

Thank you for catching this!

It makes me wonder whether the test-coverage builds should use some `sed`
invocation on the `ci/run-build-and-tests.sh` script, though, so that you
do not have to edit the Azure Pipelines definition manually all the time?

Ciao,
Dscho

Re: [PATCH v2 1/9] built-in add -p: support interactive.diffFilter

From: SZEDER Gábor <hidden>
Date: 2020-01-07 22:57:56

On Wed, Dec 25, 2019 at 11:56:52AM +0000, Johannes Schindelin via GitGitGadget wrote:

The Perl version supports post-processing the colored diff (that is
generated in addition to the uncolored diff, intended to offer a
prettier user experience) by a command configured via that config
setting, and now the built-in version does that, too.

So this patch makes the test 'detect bogus diffFilter output' in
't3701-add-interactive.sh' succeed with the builtin interactive add,
but I stumbled upon a test failure caused by SIGPIPE in an
experimental Travis CI s390x build:

  expecting success of 3701.49 'detect bogus diffFilter output': 
          git reset --hard &&
  
          echo content >test &&
          test_config interactive.diffFilter "echo too-short" &&
          printf y >y &&
          test_must_fail force_color git add -p <y
  
  + git reset --hard
  HEAD is now at 6ee5ee5 test
  + echo content
  + test_config interactive.diffFilter echo too-short
  + printf y
  + test_must_fail force_color git add -p
  test_must_fail: died by signal 13: force_color git add -p
  error: last command exited with $?=1

Turns out it's a general issue, and

  GIT_TEST_ADD_I_USE_BUILTIN=1 ./t3701-add-interactive.sh -r 39,49 --stress

fails within 10 seconds on my Linux box, whereas the scripted 'add -p'
managed to survive a couple hundred repetitions.

quoted hunk

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 12 ++++++++++++
 add-interactive.h |  3 +++
 add-patch.c       | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index a5bb14f2f4..1786ea29c4 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -52,6 +52,17 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 		diff_get_color(s->use_color, DIFF_FILE_OLD));
 	init_color(r, s, "new", s->file_new_color,
 		diff_get_color(s->use_color, DIFF_FILE_NEW));
+
+	FREE_AND_NULL(s->interactive_diff_filter);
+	git_config_get_string("interactive.difffilter",
+			      &s->interactive_diff_filter);
+}
+
+void clear_add_i_state(struct add_i_state *s)
+{
+	FREE_AND_NULL(s->interactive_diff_filter);
+	memset(s, 0, sizeof(*s));
+	s->use_color = -1;
 }
 
 /*

@@ -1149,6 +1160,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	strbuf_release(&print_file_item_data.worktree);
 	strbuf_release(&header);
 	prefix_item_list_clear(&commands);
+	clear_add_i_state(&s);
 
 	return res;
 }

diff --git a/add-interactive.h b/add-interactive.h
index b2f23479c5..46c73867ad 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -15,9 +15,12 @@ struct add_i_state {
 	char context_color[COLOR_MAXLEN];
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
+
+	char *interactive_diff_filter;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);
+void clear_add_i_state(struct add_i_state *s);
 
 struct repository;
 struct pathspec;

diff --git a/add-patch.c b/add-patch.c
index 46c6c183d5..78bde41df0 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -398,6 +398,7 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 
 	if (want_color_fd(1, -1)) {
 		struct child_process colored_cp = CHILD_PROCESS_INIT;
+		const char *diff_filter = s->s.interactive_diff_filter;
 
 		setup_child_process(s, &colored_cp, NULL);
 		xsnprintf((char *)args.argv[color_arg_index], 8, "--color");

@@ -407,6 +408,24 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		argv_array_clear(&args);
 		if (res)
 			return error(_("could not parse colored diff"));
+
+		if (diff_filter) {
+			struct child_process filter_cp = CHILD_PROCESS_INIT;
+
+			setup_child_process(s, &filter_cp,
+					    diff_filter, NULL);
+			filter_cp.git_cmd = 0;
+			filter_cp.use_shell = 1;
+			strbuf_reset(&s->buf);
+			if (pipe_command(&filter_cp,
+					 colored->buf, colored->len,
+					 &s->buf, colored->len,
+					 NULL, 0) < 0)
+				return error(_("failed to run '%s'"),
+					     diff_filter);
+			strbuf_swap(colored, &s->buf);
+		}
+
 		strbuf_complete_line(colored);
 		colored_p = colored->buf;
 		colored_pend = colored_p + colored->len;

@@ -531,6 +550,9 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 						   colored_pend - colored_p);
 			if (colored_eol)
 				colored_p = colored_eol + 1;
+			else if (p != pend)
+				/* colored shorter than non-colored? */
+				goto mismatched_output;
 			else
 				colored_p = colored_pend;

@@ -555,6 +577,15 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		 */
 		hunk->splittable_into++;
 
+	/* non-colored shorter than colored? */
+	if (colored_p != colored_pend) {
+mismatched_output:
+		error(_("mismatched output from interactive.diffFilter"));
+		advise(_("Your filter must maintain a one-to-one correspondence\n"
+			 "between its input and output lines."));
+		return -1;
+	}
+
 	return 0;
 }

@@ -1612,6 +1643,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	    parse_diff(&s, ps) < 0) {
 		strbuf_release(&s.plain);
 		strbuf_release(&s.colored);
+		clear_add_i_state(&s.s);
 		return -1;
 	}

@@ -1630,5 +1662,6 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	strbuf_release(&s.buf);
 	strbuf_release(&s.plain);
 	strbuf_release(&s.colored);
+	clear_add_i_state(&s.s);
 	return 0;
 }

-- 
gitgitgadget

Re: [PATCH v2 1/9] built-in add -p: support interactive.diffFilter

From: Johannes Schindelin <hidden>
Date: 2020-01-13 06:47:32

Hi Gábor,

On Tue, 7 Jan 2020, SZEDER Gábor wrote:

On Wed, Dec 25, 2019 at 11:56:52AM +0000, Johannes Schindelin via GitGitGadget wrote:

quoted

The Perl version supports post-processing the colored diff (that is
generated in addition to the uncolored diff, intended to offer a
prettier user experience) by a command configured via that config
setting, and now the built-in version does that, too.

So this patch makes the test 'detect bogus diffFilter output' in
't3701-add-interactive.sh' succeed with the builtin interactive add,
but I stumbled upon a test failure caused by SIGPIPE in an
experimental Travis CI s390x build:

  expecting success of 3701.49 'detect bogus diffFilter output':
          git reset --hard &&

          echo content >test &&
          test_config interactive.diffFilter "echo too-short" &&
          printf y >y &&
          test_must_fail force_color git add -p <y

  + git reset --hard
  HEAD is now at 6ee5ee5 test
  + echo content
  + test_config interactive.diffFilter echo too-short
  + printf y
  + test_must_fail force_color git add -p
  test_must_fail: died by signal 13: force_color git add -p
  error: last command exited with $?=1

Turns out it's a general issue, and

  GIT_TEST_ADD_I_USE_BUILTIN=1 ./t3701-add-interactive.sh -r 39,49 --stress

fails within 10 seconds on my Linux box, whereas the scripted 'add -p'
managed to survive a couple hundred repetitions.

You're right, of course. And I had let that slip for too long, as I saw it
sporadically happen in the Azure Pipeline, too.

This took quite a while to figure out, and I won't claim that I understand
_all_ the details: I _think_ that `stdin` being so short "breaks the pipe"
and interferes with `add -p`'s normal operation, so I needed to explicitly
use the `sigchain` feature to ignore `SIGPIPE` during `add -p`'s main
loop.

Thanks,
Dscho

[PATCH v3 01/10] built-in add -i/-p: treat SIGPIPE as EOF

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:36

From: Johannes Schindelin <redacted>

As noticed by Gábor Szeder, if we want to run `git add -p` with
redirected input through `test_must_fail` in the test suite, we must
expect that a SIGPIPE can happen due to `stdin` coming to its end.

The appropriate action here is to ignore that signal and treat it as a
regular end-of-file, otherwise the test will fail. In preparation for
such a test, introduce precisely this handling of SIGPIPE into the
built-in version of `git add -p`.

For good measure, teach the built-in `git add -i` the same trick: it
_also_ runs a loop waiting for input, and can receive a SIGPIPE just the
same (and wants to treat it as end-of-file, too).

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 3 +++
 add-patch.c       | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index a5bb14f2f4..3ff8400ea4 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -9,6 +9,7 @@
 #include "lockfile.h"
 #include "dir.h"
 #include "run-command.h"
+#include "sigchain.h"
 
 static void init_color(struct repository *r, struct add_i_state *s,
 		       const char *slot_name, char *dst,

@@ -1097,6 +1098,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 			->util = util;
 	}
 
+	sigchain_push(SIGPIPE, SIG_IGN);
 	init_add_i_state(&s, r);
 
 	/*

@@ -1149,6 +1151,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	strbuf_release(&print_file_item_data.worktree);
 	strbuf_release(&header);
 	prefix_item_list_clear(&commands);
+	sigchain_pop(SIGPIPE);
 
 	return res;
 }

diff --git a/add-patch.c b/add-patch.c
index 46c6c183d5..9a3beed72e 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -6,6 +6,7 @@
 #include "pathspec.h"
 #include "color.h"
 #include "diff.h"
+#include "sigchain.h"
 
 enum prompt_mode_type {
 	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK,

@@ -1578,6 +1579,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	};
 	size_t i, binary_count = 0;
 
+	sigchain_push(SIGPIPE, SIG_IGN);
 	init_add_i_state(&s.s, r);
 
 	if (mode == ADD_P_STASH)

@@ -1612,6 +1614,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	    parse_diff(&s, ps) < 0) {
 		strbuf_release(&s.plain);
 		strbuf_release(&s.colored);
+		sigchain_pop(SIGPIPE);
 		return -1;
 	}

@@ -1630,5 +1633,6 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	strbuf_release(&s.buf);
 	strbuf_release(&s.plain);
 	strbuf_release(&s.colored);
+	sigchain_pop(SIGPIPE);
 	return 0;
 }

-- 
gitgitgadget

[PATCH v3 02/10] built-in add -p: support interactive.diffFilter

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:37

From: Johannes Schindelin <redacted>

The Perl version supports post-processing the colored diff (that is
generated in addition to the uncolored diff, intended to offer a
prettier user experience) by a command configured via that config
setting, and now the built-in version does that, too.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 12 ++++++++++++
 add-interactive.h |  3 +++
 add-patch.c       | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index 3ff8400ea4..b36e5d97d8 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -53,6 +53,17 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 		diff_get_color(s->use_color, DIFF_FILE_OLD));
 	init_color(r, s, "new", s->file_new_color,
 		diff_get_color(s->use_color, DIFF_FILE_NEW));
+
+	FREE_AND_NULL(s->interactive_diff_filter);
+	git_config_get_string("interactive.difffilter",
+			      &s->interactive_diff_filter);
+}
+
+void clear_add_i_state(struct add_i_state *s)
+{
+	FREE_AND_NULL(s->interactive_diff_filter);
+	memset(s, 0, sizeof(*s));
+	s->use_color = -1;
 }
 
 /*

@@ -1151,6 +1162,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	strbuf_release(&print_file_item_data.worktree);
 	strbuf_release(&header);
 	prefix_item_list_clear(&commands);
+	clear_add_i_state(&s);
 	sigchain_pop(SIGPIPE);
 
 	return res;

diff --git a/add-interactive.h b/add-interactive.h
index b2f23479c5..46c73867ad 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -15,9 +15,12 @@ struct add_i_state {
 	char context_color[COLOR_MAXLEN];
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
+
+	char *interactive_diff_filter;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);
+void clear_add_i_state(struct add_i_state *s);
 
 struct repository;
 struct pathspec;

diff --git a/add-patch.c b/add-patch.c
index 9a3beed72e..7d6015229c 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -399,6 +399,7 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 
 	if (want_color_fd(1, -1)) {
 		struct child_process colored_cp = CHILD_PROCESS_INIT;
+		const char *diff_filter = s->s.interactive_diff_filter;
 
 		setup_child_process(s, &colored_cp, NULL);
 		xsnprintf((char *)args.argv[color_arg_index], 8, "--color");

@@ -408,6 +409,24 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		argv_array_clear(&args);
 		if (res)
 			return error(_("could not parse colored diff"));
+
+		if (diff_filter) {
+			struct child_process filter_cp = CHILD_PROCESS_INIT;
+
+			setup_child_process(s, &filter_cp,
+					    diff_filter, NULL);
+			filter_cp.git_cmd = 0;
+			filter_cp.use_shell = 1;
+			strbuf_reset(&s->buf);
+			if (pipe_command(&filter_cp,
+					 colored->buf, colored->len,
+					 &s->buf, colored->len,
+					 NULL, 0) < 0)
+				return error(_("failed to run '%s'"),
+					     diff_filter);
+			strbuf_swap(colored, &s->buf);
+		}
+
 		strbuf_complete_line(colored);
 		colored_p = colored->buf;
 		colored_pend = colored_p + colored->len;

@@ -532,6 +551,9 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 						   colored_pend - colored_p);
 			if (colored_eol)
 				colored_p = colored_eol + 1;
+			else if (p != pend)
+				/* colored shorter than non-colored? */
+				goto mismatched_output;
 			else
 				colored_p = colored_pend;

@@ -556,6 +578,15 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		 */
 		hunk->splittable_into++;
 
+	/* non-colored shorter than colored? */
+	if (colored_p != colored_pend) {
+mismatched_output:
+		error(_("mismatched output from interactive.diffFilter"));
+		advise(_("Your filter must maintain a one-to-one correspondence\n"
+			 "between its input and output lines."));
+		return -1;
+	}
+
 	return 0;
 }

@@ -1614,6 +1645,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	    parse_diff(&s, ps) < 0) {
 		strbuf_release(&s.plain);
 		strbuf_release(&s.colored);
+		clear_add_i_state(&s.s);
 		sigchain_pop(SIGPIPE);
 		return -1;
 	}

@@ -1633,6 +1665,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	strbuf_release(&s.buf);
 	strbuf_release(&s.plain);
 	strbuf_release(&s.colored);
+	clear_add_i_state(&s.s);
 	sigchain_pop(SIGPIPE);
 	return 0;
 }

-- 
gitgitgadget

[PATCH v3 03/10] built-in add -p: handle diff.algorithm

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:38

From: Johannes Schindelin <redacted>

The Perl version of `git add -p` reads the config setting
`diff.algorithm` and if set, uses it to generate the diff using the
specified algorithm.

This patch ports that functionality to the C version.

Note: just like `git-add--interactive.perl`, we do _not_ respect this
config setting in `git add -i`'s `diff` command, but _only_ in the
`patch` command.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 5 +++++
 add-interactive.h | 2 +-
 add-patch.c       | 3 +++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/add-interactive.c b/add-interactive.c
index b36e5d97d8..e3cc30ad24 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -57,11 +57,16 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	FREE_AND_NULL(s->interactive_diff_filter);
 	git_config_get_string("interactive.difffilter",
 			      &s->interactive_diff_filter);
+
+	FREE_AND_NULL(s->interactive_diff_algorithm);
+	git_config_get_string("diff.algorithm",
+			      &s->interactive_diff_algorithm);
 }
 
 void clear_add_i_state(struct add_i_state *s)
 {
 	FREE_AND_NULL(s->interactive_diff_filter);
+	FREE_AND_NULL(s->interactive_diff_algorithm);
 	memset(s, 0, sizeof(*s));
 	s->use_color = -1;
 }

diff --git a/add-interactive.h b/add-interactive.h
index 46c73867ad..923efaf527 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -16,7 +16,7 @@ struct add_i_state {
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
 
-	char *interactive_diff_filter;
+	char *interactive_diff_filter, *interactive_diff_algorithm;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);

diff --git a/add-patch.c b/add-patch.c
index 7d6015229c..736bcb4aa7 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -361,6 +361,7 @@ static int is_octal(const char *p, size_t len)
 static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 {
 	struct argv_array args = ARGV_ARRAY_INIT;
+	const char *diff_algorithm = s->s.interactive_diff_algorithm;
 	struct strbuf *plain = &s->plain, *colored = NULL;
 	struct child_process cp = CHILD_PROCESS_INIT;
 	char *p, *pend, *colored_p = NULL, *colored_pend = NULL, marker = '\0';

@@ -370,6 +371,8 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 	int res;
 
 	argv_array_pushv(&args, s->mode->diff_cmd);
+	if (diff_algorithm)
+		argv_array_pushf(&args, "--diff-algorithm=%s", diff_algorithm);
 	if (s->revision) {
 		struct object_id oid;
 		argv_array_push(&args,

-- 
gitgitgadget

[PATCH v3 00/10] built-in add -p: add support for the same config settings as the Perl version

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:39

This is the final leg of the journey to a fully built-in git add: the git
add -i and git add -p modes were re-implemented in C, but they lacked
support for a couple of config settings.

The one that sticks out most is the interactive.singleKey setting: it was
particularly hard to get to work, especially on Windows.

It also seems to be the setting that is incomplete already in the Perl
version of the interactive add command: while the name of the config setting
suggests that it applies to all of the interactive add, including the main
loop of git add --interactive and to the file selections in that command, it
does not. Only the git add --patch mode respects that setting.

As it is outside the purpose of the conversion of git-add--interactive.perl 
to C, we will leave that loose end for some future date.

Changes since v2:

 * Fixed the SIGPIPE issue pointed out by Gábor Szeder.

Changes since v1:

 * Fixed the commit message where a copy/paste fail made it talk about
   another GIT_TEST_* variable than the GIT_TEST_ADD_I_USE_BUILTIN one.

Johannes Schindelin (10):
  built-in add -i/-p: treat SIGPIPE as EOF
  built-in add -p: support interactive.diffFilter
  built-in add -p: handle diff.algorithm
  terminal: make the code of disable_echo() reusable
  terminal: accommodate Git for Windows' default terminal
  terminal: add a new function to read a single keystroke
  built-in add -p: respect the `interactive.singlekey` config setting
  built-in add -p: handle Escape sequences in interactive.singlekey mode
  built-in add -p: handle Escape sequences more efficiently
  ci: include the built-in `git add -i` in the `linux-gcc` job

 add-interactive.c         |  22 ++++
 add-interactive.h         |   4 +
 add-patch.c               |  61 +++++++++-
 ci/run-build-and-tests.sh |   1 +
 compat/terminal.c         | 249 +++++++++++++++++++++++++++++++++++++-
 compat/terminal.h         |   3 +
 6 files changed, 332 insertions(+), 8 deletions(-)


base-commit: c480eeb574e649a19f27dc09a994e45f9b2c2622
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-175%2Fdscho%2Fadd-p-in-c-config-settings-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-175/dscho/add-p-in-c-config-settings-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/175

Range-diff vs v2:

  -:  ---------- >  1:  5e258a8d2b built-in add -i/-p: treat SIGPIPE as EOF
  1:  f45ff08bd0 !  2:  2a5951ecfe built-in add -p: support interactive.diffFilter
     @@ -35,9 +35,9 @@
       	strbuf_release(&header);
       	prefix_item_list_clear(&commands);
      +	clear_add_i_state(&s);
     + 	sigchain_pop(SIGPIPE);
       
       	return res;
     - }
      
       diff --git a/add-interactive.h b/add-interactive.h
       --- a/add-interactive.h
     @@ -123,13 +123,14 @@
       		strbuf_release(&s.plain);
       		strbuf_release(&s.colored);
      +		clear_add_i_state(&s.s);
     + 		sigchain_pop(SIGPIPE);
       		return -1;
       	}
     - 
      @@
       	strbuf_release(&s.buf);
       	strbuf_release(&s.plain);
       	strbuf_release(&s.colored);
      +	clear_add_i_state(&s.s);
     + 	sigchain_pop(SIGPIPE);
       	return 0;
       }
  2:  e9c4a13cbf =  3:  a2bce01818 built-in add -p: handle diff.algorithm
  3:  e643554dba =  4:  be40a37c0c terminal: make the code of disable_echo() reusable
  4:  bd2306c5d5 =  5:  233f23791c terminal: accommodate Git for Windows' default terminal
  5:  190fb4f5e9 =  6:  74593b5115 terminal: add a new function to read a single keystroke
  6:  167dfa37dd !  7:  197fe1e14a built-in add -p: respect the `interactive.singlekey` config setting
     @@ -48,9 +48,9 @@
       --- a/add-patch.c
       +++ b/add-patch.c
      @@
     - #include "pathspec.h"
       #include "color.h"
       #include "diff.h"
     + #include "sigchain.h"
      +#include "compat/terminal.h"
       
       enum prompt_mode_type {
  7:  32067bebe8 =  8:  9ab381d539 built-in add -p: handle Escape sequences in interactive.singlekey mode
  8:  703719ffce =  9:  bdb6268b8b built-in add -p: handle Escape sequences more efficiently
  9:  23a3a47b01 = 10:  c4195969a6 ci: include the built-in `git add -i` in the `linux-gcc` job

-- 
gitgitgadget

[PATCH v3 05/10] terminal: accommodate Git for Windows' default terminal

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:40

From: Johannes Schindelin <redacted>

Git for Windows' Git Bash runs in MinTTY by default, which does not have
a Win32 Console instance, but uses MSYS2 pseudo terminals instead.

This is a problem, as Git for Windows does not want to use the MSYS2
emulation layer for Git itself, and therefore has no direct way to
interact with that pseudo terminal.

As a workaround, use the `stty` utility (which is included in Git for
Windows, and which *is* an MSYS2 program, so it knows how to deal with
the pseudo terminal).

Note: If Git runs in a regular CMD or PowerShell window, there *is* a
regular Win32 Console to work with. This is not a problem for the MSYS2
`stty`: it copes with this scenario just fine.

Also note that we introduce support for more bits than would be
necessary for a mere `disable_echo()` here, in preparation for the
upcoming `enable_non_canonical()` function.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/compat/terminal.c b/compat/terminal.c
index 1fb40b3a0a..16e9949da1 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -2,6 +2,8 @@
 #include "compat/terminal.h"
 #include "sigchain.h"
 #include "strbuf.h"
+#include "run-command.h"
+#include "string-list.h"
 
 #if defined(HAVE_DEV_TTY) || defined(GIT_WINDOWS_NATIVE)

@@ -64,11 +66,28 @@ static int disable_echo(void)
 #define OUTPUT_PATH "CONOUT$"
 #define FORCE_TEXT "t"
 
+static int use_stty = 1;
+static struct string_list stty_restore = STRING_LIST_INIT_DUP;
 static HANDLE hconin = INVALID_HANDLE_VALUE;
 static DWORD cmode;
 
 static void restore_term(void)
 {
+	if (use_stty) {
+		int i;
+		struct child_process cp = CHILD_PROCESS_INIT;
+
+		if (stty_restore.nr == 0)
+			return;
+
+		argv_array_push(&cp.args, "stty");
+		for (i = 0; i < stty_restore.nr; i++)
+			argv_array_push(&cp.args, stty_restore.items[i].string);
+		run_command(&cp);
+		string_list_clear(&stty_restore, 0);
+		return;
+	}
+
 	if (hconin == INVALID_HANDLE_VALUE)
 		return;

@@ -79,6 +98,37 @@ static void restore_term(void)
 
 static int disable_bits(DWORD bits)
 {
+	if (use_stty) {
+		struct child_process cp = CHILD_PROCESS_INIT;
+
+		argv_array_push(&cp.args, "stty");
+
+		if (bits & ENABLE_LINE_INPUT) {
+			string_list_append(&stty_restore, "icanon");
+			argv_array_push(&cp.args, "-icanon");
+		}
+
+		if (bits & ENABLE_ECHO_INPUT) {
+			string_list_append(&stty_restore, "echo");
+			argv_array_push(&cp.args, "-echo");
+		}
+
+		if (bits & ENABLE_PROCESSED_INPUT) {
+			string_list_append(&stty_restore, "-ignbrk");
+			string_list_append(&stty_restore, "intr");
+			string_list_append(&stty_restore, "^c");
+			argv_array_push(&cp.args, "ignbrk");
+			argv_array_push(&cp.args, "intr");
+			argv_array_push(&cp.args, "");
+		}
+
+		if (run_command(&cp) == 0)
+			return 0;
+
+		/* `stty` could not be executed; access the Console directly */
+		use_stty = 0;
+	}
+
 	hconin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
 	    FILE_SHARE_READ, NULL, OPEN_EXISTING,
 	    FILE_ATTRIBUTE_NORMAL, NULL);

-- 
gitgitgadget

[PATCH v3 04/10] terminal: make the code of disable_echo() reusable

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:42

From: Johannes Schindelin <redacted>

We are about to introduce the function `enable_non_canonical()`, which
shares almost the complete code with `disable_echo()`.

Let's prepare for that, by refactoring out that shared code.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index fa13ee672d..1fb40b3a0a 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -32,7 +32,7 @@ static void restore_term(void)
 	term_fd = -1;
 }
 
-static int disable_echo(void)
+static int disable_bits(tcflag_t bits)
 {
 	struct termios t;

@@ -43,7 +43,7 @@ static int disable_echo(void)
 	old_term = t;
 	sigchain_push_common(restore_term_on_signal);
 
-	t.c_lflag &= ~ECHO;
+	t.c_lflag &= ~bits;
 	if (!tcsetattr(term_fd, TCSAFLUSH, &t))
 		return 0;

@@ -53,6 +53,11 @@ static int disable_echo(void)
 	return -1;
 }
 
+static int disable_echo(void)
+{
+	return disable_bits(ECHO);
+}
+
 #elif defined(GIT_WINDOWS_NATIVE)
 
 #define INPUT_PATH "CONIN$"

@@ -72,7 +77,7 @@ static void restore_term(void)
 	hconin = INVALID_HANDLE_VALUE;
 }
 
-static int disable_echo(void)
+static int disable_bits(DWORD bits)
 {
 	hconin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
 	    FILE_SHARE_READ, NULL, OPEN_EXISTING,

@@ -82,7 +87,7 @@ static int disable_echo(void)
 
 	GetConsoleMode(hconin, &cmode);
 	sigchain_push_common(restore_term_on_signal);
-	if (!SetConsoleMode(hconin, cmode & (~ENABLE_ECHO_INPUT))) {
+	if (!SetConsoleMode(hconin, cmode & ~bits)) {
 		CloseHandle(hconin);
 		hconin = INVALID_HANDLE_VALUE;
 		return -1;

@@ -91,6 +96,12 @@ static int disable_echo(void)
 	return 0;
 }
 
+static int disable_echo(void)
+{
+	return disable_bits(ENABLE_ECHO_INPUT);
+}
+
+
 #endif
 
 #ifndef FORCE_TEXT

-- 
gitgitgadget

[PATCH v3 06/10] terminal: add a new function to read a single keystroke

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:43

From: Johannes Schindelin <redacted>

Typically, input on the command-line is line-based. It is actually not
really easy to get single characters (or better put: keystrokes).

We provide two implementations here:

- One that handles `/dev/tty` based systems as well as native Windows.
  The former uses the `tcsetattr()` function to put the terminal into
  "raw mode", which allows us to read individual keystrokes, one by one.
  The latter uses `stty.exe` to do the same, falling back to direct
  Win32 Console access.

  Thanks to the refactoring leading up to this commit, this is a single
  function, with the platform-specific details hidden away in
  conditionally-compiled code blocks.

- A fall-back which simply punts and reads back an entire line.

Note that the function writes the keystroke into an `strbuf` rather than
a `char`, in preparation for reading Escape sequences (e.g. when the
user hit an arrow key). This is also required for UTF-8 sequences in
case the keystroke corresponds to a non-ASCII letter.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++
 compat/terminal.h |  3 +++
 2 files changed, 58 insertions(+)

diff --git a/compat/terminal.c b/compat/terminal.c
index 16e9949da1..1b2564042a 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -60,6 +60,11 @@ static int disable_echo(void)
 	return disable_bits(ECHO);
 }
 
+static int enable_non_canonical(void)
+{
+	return disable_bits(ICANON | ECHO);
+}
+
 #elif defined(GIT_WINDOWS_NATIVE)
 
 #define INPUT_PATH "CONIN$"

@@ -151,6 +156,10 @@ static int disable_echo(void)
 	return disable_bits(ENABLE_ECHO_INPUT);
 }
 
+static int enable_non_canonical(void)
+{
+	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
+}
 
 #endif

@@ -198,6 +207,33 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+int read_key_without_echo(struct strbuf *buf)
+{
+	static int warning_displayed;
+	int ch;
+
+	if (warning_displayed || enable_non_canonical() < 0) {
+		if (!warning_displayed) {
+			warning("reading single keystrokes not supported on "
+				"this platform; reading line instead");
+			warning_displayed = 1;
+		}
+
+		return strbuf_getline(buf, stdin);
+	}
+
+	strbuf_reset(buf);
+	ch = getchar();
+	if (ch == EOF) {
+		restore_term();
+		return EOF;
+	}
+
+	strbuf_addch(buf, ch);
+	restore_term();
+	return 0;
+}
+
 #else
 
 char *git_terminal_prompt(const char *prompt, int echo)

@@ -205,4 +241,23 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return getpass(prompt);
 }
 
+int read_key_without_echo(struct strbuf *buf)
+{
+	static int warning_displayed;
+	const char *res;
+
+	if (!warning_displayed) {
+		warning("reading single keystrokes not supported on this "
+			"platform; reading line instead");
+		warning_displayed = 1;
+	}
+
+	res = getpass("");
+	strbuf_reset(buf);
+	if (!res)
+		return EOF;
+	strbuf_addstr(buf, res);
+	return 0;
+}
+
 #endif

diff --git a/compat/terminal.h b/compat/terminal.h
index 97db7cd69d..a9d52b8464 100644
--- a/compat/terminal.h
+++ b/compat/terminal.h

@@ -3,4 +3,7 @@
 
 char *git_terminal_prompt(const char *prompt, int echo);
 
+/* Read a single keystroke, without echoing it to the terminal */
+int read_key_without_echo(struct strbuf *buf);
+
 #endif /* COMPAT_TERMINAL_H */

-- 
gitgitgadget

[PATCH v3 07/10] built-in add -p: respect the `interactive.singlekey` config setting

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:45

From: Johannes Schindelin <redacted>

The Perl version of `git add -p` supports this config setting to allow
users to input commands via single characters (as opposed to having to
press the <Enter> key afterwards).

This is an opt-in feature because it requires Perl packages
(Term::ReadKey and Term::Cap, where it tries to handle an absence of the
latter package gracefully) to work. Note that at least on Ubuntu, that
Perl package is not installed by default (it needs to be installed via
`sudo apt-get install libterm-readkey-perl`), so this feature is
probably not used a whole lot.

In C, we obviously do not have these packages available, but we just
introduced `read_single_keystroke()` that is similar to what
Term::ReadKey provides, and we use that here.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c |  2 ++
 add-interactive.h |  1 +
 add-patch.c       | 21 +++++++++++++++++----
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index e3cc30ad24..bb6acf5ef6 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -61,6 +61,8 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	FREE_AND_NULL(s->interactive_diff_algorithm);
 	git_config_get_string("diff.algorithm",
 			      &s->interactive_diff_algorithm);
+
+	git_config_get_bool("interactive.singlekey", &s->use_single_key);
 }
 
 void clear_add_i_state(struct add_i_state *s)

diff --git a/add-interactive.h b/add-interactive.h
index 923efaf527..693f125e8e 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -16,6 +16,7 @@ struct add_i_state {
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
 
+	int use_single_key;
 	char *interactive_diff_filter, *interactive_diff_algorithm;
 };

diff --git a/add-patch.c b/add-patch.c
index 736bcb4aa7..67741128a8 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -7,6 +7,7 @@
 #include "color.h"
 #include "diff.h"
 #include "sigchain.h"
+#include "compat/terminal.h"
 
 enum prompt_mode_type {
 	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK,

@@ -1150,14 +1151,27 @@ static int run_apply_check(struct add_p_state *s,
 	return 0;
 }
 
+static int read_single_character(struct add_p_state *s)
+{
+	if (s->s.use_single_key) {
+		int res = read_key_without_echo(&s->answer);
+		printf("%s\n", res == EOF ? "" : s->answer.buf);
+		return res;
+	}
+
+	if (strbuf_getline(&s->answer, stdin) == EOF)
+		return EOF;
+	strbuf_trim_trailing_newline(&s->answer);
+	return 0;
+}
+
 static int prompt_yesno(struct add_p_state *s, const char *prompt)
 {
 	for (;;) {
 		color_fprintf(stdout, s->s.prompt_color, "%s", _(prompt));
 		fflush(stdout);
-		if (strbuf_getline(&s->answer, stdin) == EOF)
+		if (read_single_character(s) == EOF)
 			return -1;
-		strbuf_trim_trailing_newline(&s->answer);
 		switch (tolower(s->answer.buf[0])) {
 		case 'n': return 0;
 		case 'y': return 1;

@@ -1397,9 +1411,8 @@ static int patch_update_file(struct add_p_state *s,
 			      _(s->mode->prompt_mode[prompt_mode_type]),
 			      s->buf.buf);
 		fflush(stdout);
-		if (strbuf_getline(&s->answer, stdin) == EOF)
+		if (read_single_character(s) == EOF)
 			break;
-		strbuf_trim_trailing_newline(&s->answer);
 
 		if (!s->answer.len)
 			continue;

-- 
gitgitgadget

[PATCH v3 10/10] ci: include the built-in `git add -i` in the `linux-gcc` job

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:46

From: Johannes Schindelin <redacted>

This job runs the test suite twice, once in regular mode, and once with
a whole slew of `GIT_TEST_*` variables set.

Now that the built-in version of `git add --interactive` is
feature-complete, let's also throw `GIT_TEST_ADD_I_USE_BUILTIN` into
that fray.

Signed-off-by: Johannes Schindelin <redacted>
---
 ci/run-build-and-tests.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index ff0ef7f08e..4df54c4efe 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh

@@ -20,6 +20,7 @@ linux-gcc)
 	export GIT_TEST_OE_DELTA_SIZE=5
 	export GIT_TEST_COMMIT_GRAPH=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
+	export GIT_TEST_ADD_I_USE_BUILTIN=1
 	make test
 	;;
 linux-gcc-4.8)

-- 
gitgitgadget

[PATCH v3 09/10] built-in add -p: handle Escape sequences more efficiently

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:47

From: Johannes Schindelin <redacted>

When `interactive.singlekey = true`, we react immediately to keystrokes,
even to Escape sequences (e.g. when pressing a cursor key).

The problem with Escape sequences is that we do not really know when
they are done, and as a heuristic we poll standard input for half a
second to make sure that we got all of it.

While waiting half a second is not asking for a whole lot, it can become
quite annoying over time, therefore with this patch, we read the
terminal capabilities (if available) and extract known Escape sequences
from there, then stop polling immediately when we detected that the user
pressed a key that generated such a known sequence.

This recapitulates the remaining part of b5cc003253c8 (add -i: ignore
terminal escape sequences, 2011-05-17).

Note: We do *not* query the terminal capabilities directly. That would
either require a lot of platform-specific code, or it would require
linking to a library such as ncurses.

Linking to a library in the built-ins is something we try very hard to
avoid (we even kicked the libcurl dependency to a non-built-in remote
helper, just to shave off a tiny fraction of a second from Git's startup
time). And the platform-specific code would be a maintenance nightmare.

Even worse: in Git for Windows' case, we would need to query MSYS2
pseudo terminals, which `git.exe` simply cannot do (because it is
intentionally *not* an MSYS2 program).

To address this, we simply spawn `infocmp -L -1` and parse its output
(which works even in Git for Windows, because that helper is included in
the end-user facing installations).

This is done only once, as in the Perl version, but it is done only when
the first Escape sequence is encountered, not upon startup of `git add
-i`; This saves on startup time, yet makes reacting to the first Escape
sequence slightly more sluggish. But it allows us to keep the
terminal-related code encapsulated in the `compat/terminal.c` file.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index b7f58d1781..35bca03d14 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -4,6 +4,7 @@
 #include "strbuf.h"
 #include "run-command.h"
 #include "string-list.h"
+#include "hashmap.h"
 
 #if defined(HAVE_DEV_TTY) || defined(GIT_WINDOWS_NATIVE)

@@ -238,6 +239,71 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+/*
+ * The `is_known_escape_sequence()` function returns 1 if the passed string
+ * corresponds to an Escape sequence that the terminal capabilities contains.
+ *
+ * To avoid depending on ncurses or other platform-specific libraries, we rely
+ * on the presence of the `infocmp` executable to do the job for us (failing
+ * silently if the program is not available or refused to run).
+ */
+struct escape_sequence_entry {
+	struct hashmap_entry entry;
+	char sequence[FLEX_ARRAY];
+};
+
+static int sequence_entry_cmp(const void *hashmap_cmp_fn_data,
+			      const struct escape_sequence_entry *e1,
+			      const struct escape_sequence_entry *e2,
+			      const void *keydata)
+{
+	return strcmp(e1->sequence, keydata ? keydata : e2->sequence);
+}
+
+static int is_known_escape_sequence(const char *sequence)
+{
+	static struct hashmap sequences;
+	static int initialized;
+
+	if (!initialized) {
+		struct child_process cp = CHILD_PROCESS_INIT;
+		struct strbuf buf = STRBUF_INIT;
+		char *p, *eol;
+
+		hashmap_init(&sequences, (hashmap_cmp_fn)sequence_entry_cmp,
+			     NULL, 0);
+
+		argv_array_pushl(&cp.args, "infocmp", "-L", "-1", NULL);
+		if (pipe_command(&cp, NULL, 0, &buf, 0, NULL, 0))
+			strbuf_setlen(&buf, 0);
+
+		for (eol = p = buf.buf; *p; p = eol + 1) {
+			p = strchr(p, '=');
+			if (!p)
+				break;
+			p++;
+			eol = strchrnul(p, '\n');
+
+			if (starts_with(p, "\\E")) {
+				char *comma = memchr(p, ',', eol - p);
+				struct escape_sequence_entry *e;
+
+				p[0] = '^';
+				p[1] = '[';
+				FLEX_ALLOC_MEM(e, sequence, p, comma - p);
+				hashmap_entry_init(&e->entry,
+						   strhash(e->sequence));
+				hashmap_add(&sequences, &e->entry);
+			}
+			if (!*eol)
+				break;
+		}
+		initialized = 1;
+	}
+
+	return !!hashmap_get_from_hash(&sequences, strhash(sequence), sequence);
+}
+
 int read_key_without_echo(struct strbuf *buf)
 {
 	static int warning_displayed;

@@ -271,7 +337,12 @@ int read_key_without_echo(struct strbuf *buf)
 		 * Start by replacing the Escape byte with ^[ */
 		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
 
-		for (;;) {
+		/*
+		 * Query the terminal capabilities once about all the Escape
+		 * sequences it knows about, so that we can avoid waiting for
+		 * half a second when we know that the sequence is complete.
+		 */
+		while (!is_known_escape_sequence(buf->buf)) {
 			struct pollfd pfd = { .fd = 0, .events = POLLIN };
 
 			if (poll(&pfd, 1, 500) < 1)

-- 
gitgitgadget

[PATCH v3 08/10] built-in add -p: handle Escape sequences in interactive.singlekey mode

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-13 08:29:48

From: Johannes Schindelin <redacted>

This recapitulates part of b5cc003253c8 (add -i: ignore terminal escape
sequences, 2011-05-17):

    add -i: ignore terminal escape sequences

    On the author's terminal, the up-arrow input sequence is ^[[A, and
    thus fat-fingering an up-arrow into 'git checkout -p' is quite
    dangerous: git-add--interactive.perl will ignore the ^[ and [
    characters and happily treat A as "discard everything".

    As a band-aid fix, use Term::Cap to get all terminal capabilities.
    Then use the heuristic that any capability value that starts with ^[
    (i.e., \e in perl) must be a key input sequence.  Finally, given an
    input that starts with ^[, read more characters until we have read a
    full escape sequence, then return that to the caller.  We use a
    timeout of 0.5 seconds on the subsequent reads to avoid getting stuck
    if the user actually input a lone ^[.

    Since none of the currently recognized keys start with ^[, the net
    result is that the sequence as a whole will be ignored and the help
    displayed.

Note that we leave part for later which uses "Term::Cap to get all
terminal capabilities", for several reasons:

1. it is actually not really necessary, as the timeout of 0.5 seconds
   should be plenty sufficient to catch Escape sequences,

2. it is cleaner to keep the change to special-case Escape sequences
   separate from the change that reads all terminal capabilities to
   speed things up, and

3. in practice, relying on the terminal capabilities is a bit overrated,
   as the information could be incomplete, or plain wrong. For example,
   in this developer's tmux sessions, the terminal capabilities claim
   that the "cursor up" sequence is ^[M, but the actual sequence
   produced by the "cursor up" key is ^[[A.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index 1b2564042a..b7f58d1781 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -161,6 +161,37 @@ static int enable_non_canonical(void)
 	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
 }
 
+/*
+ * Override `getchar()`, as the default implementation does not use
+ * `ReadFile()`.
+ *
+ * This poses a problem when we want to see whether the standard
+ * input has more characters, as the default of Git for Windows is to start the
+ * Bash in a MinTTY, which uses a named pipe to emulate a pty, in which case
+ * our `poll()` emulation calls `PeekNamedPipe()`, which seems to require
+ * `ReadFile()` to be called first to work properly (it only reports 0
+ * available bytes, otherwise).
+ *
+ * So let's just override `getchar()` with a version backed by `ReadFile()` and
+ * go our merry ways from here.
+ */
+static int mingw_getchar(void)
+{
+	DWORD read = 0;
+	unsigned char ch;
+
+	if (!ReadFile(GetStdHandle(STD_INPUT_HANDLE), &ch, 1, &read, NULL))
+		return EOF;
+
+	if (!read) {
+		error("Unexpected 0 read");
+		return EOF;
+	}
+
+	return ch;
+}
+#define getchar mingw_getchar
+
 #endif
 
 #ifndef FORCE_TEXT

@@ -228,8 +259,31 @@ int read_key_without_echo(struct strbuf *buf)
 		restore_term();
 		return EOF;
 	}
-
 	strbuf_addch(buf, ch);
+
+	if (ch == '\033' /* ESC */) {
+		/*
+		 * We are most likely looking at an Escape sequence. Let's try
+		 * to read more bytes, waiting at most half a second, assuming
+		 * that the sequence is complete if we did not receive any byte
+		 * within that time.
+		 *
+		 * Start by replacing the Escape byte with ^[ */
+		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
+
+		for (;;) {
+			struct pollfd pfd = { .fd = 0, .events = POLLIN };
+
+			if (poll(&pfd, 1, 500) < 1)
+				break;
+
+			ch = getchar();
+			if (ch == EOF)
+				return 0;
+			strbuf_addch(buf, ch);
+		}
+	}
+
 	restore_term();
 	return 0;
 }

-- 
gitgitgadget

Re: [PATCH v3 01/10] built-in add -i/-p: treat SIGPIPE as EOF

From: SZEDER Gábor <hidden>
Date: 2020-01-13 17:04:25

On Mon, Jan 13, 2020 at 08:29:22AM +0000, Johannes Schindelin via GitGitGadget wrote:

From: Johannes Schindelin <redacted>

As noticed by Gábor Szeder, if we want to run `git add -p` with
redirected input through `test_must_fail` in the test suite, we must
expect that a SIGPIPE can happen due to `stdin` coming to its end.

I don't think this issue is related to the redirected input: I
modified that flaky test to send "unlimited" data to 'git add's stdin,
i.e.:

  /usr/bin/yes | test_must_fail force_color git add -p

and the test with --stress still failed with SIGPIPE all the same and
just as fast.

After looking into it, the issue seems to be sending data to the
broken diffFilter process.  So in that test the diff is "filtered"
through 'echo too-short', which exits real fast, and doesn't read its
standard input at all (well, apart from e.g. the usual kernel
buffering that might happen on a pipe between the two processes).
Making sure that the diffFilter process reads all the data before
exiting, i.e. changing it to:

  test_config interactive.diffFilter "cat >/dev/null ; echo too-short" &&

made the test reliable, with over 2000 --stress repetitions, and that
with only a single "y" on 'git add's stdin.

Now, merely tweaking the test is clearly insufficient, because we not
only want the test to be realiable, but we want 'git add' to die
gracefully when users out there mess up their configuration.

Ignoring SIGPIPE can surely accomplish that, but I'm not sure about
the scope.  I mean your patch seems to ignore SIGPIPE basically for
almost the whole 'git add -(i|p)' process, but perhaps it should be
limited only to the surroundings of the pipe_command() call running
the diffFilter, and be done as part of the next patch adding the 'if
(diff_filter)' block.

Furthermore, I'm worried that by simply ignoring SIGPIPE we might just
ignore a more fundamental issue in pipe_command(): shouldn't that
function be smart enough not to write() to a fd that has no one on the
other side to read it in the first place?!

So, when the diffFilter process exits unexpectedly early, then the
poll() call in pipe_command() -> pump_io() -> pump_io_round() returns
with success and usually sets 'revents' for the child process' stdin
to 12 (i.e. 'POLLOUT | POLLERR'; gah, how I hate unnamed constants :).
Unfortunately, at that point we don't take any special action on
POLLERR, but call xwrite() to try to write to the dead fd anyway,
which then promptly triggers SIGPIPE.  (This is what usually happens
when stepping through the statements of those functions in a debugger,
and the diffFilter process has all the time in the world to exit.)

We could handle POLLERR with a patch like this:

  --- >8 ---

Subject: run-command: handle POLLERR in pump_io_round() to reduce risk of SIGPIPE

diff --git a/run-command.c b/run-command.c
index 3449db319b..57093f0acc 100644
--- a/run-command.c
+++ b/run-command.c

@@ -1416,25 +1416,31 @@ static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
 	if (poll(pfd, pollsize, -1) < 0) {
 		if (errno == EINTR)
 			return 1;
 		die_errno("poll failed");
 	}
 
 	for (i = 0; i < nr; i++) {
 		struct io_pump *io = &slots[i];
 
 		if (io->fd < 0)
 			continue;
 
-		if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
+		if (io->pfd->revents & POLLERR) {
+			io->error = ECONNRESET;  /* What should we report to the caller? */
+			close(io->fd);
+			io->fd = -1;
+			continue;
+		}
+		if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLNVAL)))
 			continue;
 
 		if (io->type == POLLOUT) {
 			ssize_t len = xwrite(io->fd,
 					     io->u.out.buf, io->u.out.len);
 			if (len < 0) {
 				io->error = errno;
 				close(io->fd);
 				io->fd = -1;
 			} else {
 				io->u.out.buf += len;
 				io->u.out.len -= len;

  --- >8 ---

Unfortunately #1, this changes the error 'git add -p' dies with from:

  error: mismatched output from interactive.diffFilter

to:

  error: failed to run 'echo too-short'

It might affect other commands as well, but FWIW the test suite
doesn't catch any.


Unfortunately #2, the above patch doesn't completely eliminates the
SIGPIPE, but only (greatly) reduces its probability.  It is possible
that:

  - poll() returns with success and indicating a writable fd without
    any error, i.e. 'revents = 4'.

  - the bogus diffFilter exits, closing its stdin.

  - 'git add' attempts to xwrite() to the now closed fd, and triggers
    a SIGPIPE right away.

This happens much rarer, 'GIT_TEST_ADD_I_USE_BUILTIN=1
./t3701-add-interactive.sh -r 39,49 --stress-jobs=<4*nr-of-cores>
--stress' tends to take over 200 repetitions.  The patch below
reproduces it fairly reliably by adding two strategically-placed
sleep()s, with a bit of extra debug output:

  --- >8 ---

diff --git a/add-patch.c b/add-patch.c
index d8dafa8168..0fd017bbd3 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -421,6 +421,7 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 			filter_cp.git_cmd = 0;
 			filter_cp.use_shell = 1;
 			strbuf_reset(&s->buf);
+			fprintf(stderr, "about to run diffFilter\n");
 			if (pipe_command(&filter_cp,
 					 colored->buf, colored->len,
 					 &s->buf, colored->len,

diff --git a/run-command.c b/run-command.c
index 57093f0acc..49ae88a922 100644
--- a/run-command.c
+++ b/run-command.c

@@ -1419,6 +1419,7 @@ static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
 		die_errno("poll failed");
 	}
 
+	sleep(2);
 	for (i = 0; i < nr; i++) {
 		struct io_pump *io = &slots[i];

@@ -1435,8 +1436,11 @@ static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
 			continue;
 
 		if (io->type == POLLOUT) {
-			ssize_t len = xwrite(io->fd,
+			ssize_t len;
+			fprintf(stderr, "attempting to xwrite() %lu bytes to a fd with revents flags 0x%hx\n", io->u.out.len, io->pfd->revents);
+			len = xwrite(io->fd,
 					     io->u.out.buf, io->u.out.len);
+			fprintf(stderr, "after xwrite()\n");
 			if (len < 0) {
 				io->error = errno;
 				close(io->fd);

diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index 12ee321707..acffc9af37 100755
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh

@@ -561,7 +561,7 @@ test_expect_success 'detect bogus diffFilter output' '
 	git reset --hard &&
 
 	echo content >test &&
-	test_config interactive.diffFilter "echo too-short" &&
+	test_config interactive.diffFilter "sleep 1 ; echo too-short" &&
 	printf y >y &&
 	test_must_fail force_color git add -p <y
 '

  --- >8 ---

and 'GIT_TEST_ADD_I_USE_BUILTIN=1 ./t3701-add-interactive.sh -r 39,49'
fails with:

  + test_must_fail force_color git add -p
  about to run diffFilter
  attempting to xwrite() 224 bytes to a fd with revents flags 0x4
  test_must_fail: died by signal 13: force_color git add -p

I don't understand why we get SIGPIPE right away instead of some error
that we can act upon (ECONNRESET?).  FWIW, it fails the same way not
only on my box, but on Travis CI's Linux and OSX images as well.

  https://travis-ci.org/szeder/git/jobs/636446843#L2937


Cc'ing Peff for all things SIGPIPE :) who also happens to be the
author of both pipe_command() and that now flaky test.

quoted hunk

The appropriate action here is to ignore that signal and treat it as a
regular end-of-file, otherwise the test will fail. In preparation for
such a test, introduce precisely this handling of SIGPIPE into the
built-in version of `git add -p`.

For good measure, teach the built-in `git add -i` the same trick: it
_also_ runs a loop waiting for input, and can receive a SIGPIPE just the
same (and wants to treat it as end-of-file, too).

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 3 +++
 add-patch.c       | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index a5bb14f2f4..3ff8400ea4 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -9,6 +9,7 @@
 #include "lockfile.h"
 #include "dir.h"
 #include "run-command.h"
+#include "sigchain.h"
 
 static void init_color(struct repository *r, struct add_i_state *s,
 		       const char *slot_name, char *dst,

@@ -1097,6 +1098,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 			->util = util;
 	}
 
+	sigchain_push(SIGPIPE, SIG_IGN);
 	init_add_i_state(&s, r);
 
 	/*

@@ -1149,6 +1151,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	strbuf_release(&print_file_item_data.worktree);
 	strbuf_release(&header);
 	prefix_item_list_clear(&commands);
+	sigchain_pop(SIGPIPE);
 
 	return res;
 }

diff --git a/add-patch.c b/add-patch.c
index 46c6c183d5..9a3beed72e 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -6,6 +6,7 @@
 #include "pathspec.h"
 #include "color.h"
 #include "diff.h"
+#include "sigchain.h"
 
 enum prompt_mode_type {
 	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK,

@@ -1578,6 +1579,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	};
 	size_t i, binary_count = 0;
 
+	sigchain_push(SIGPIPE, SIG_IGN);
 	init_add_i_state(&s.s, r);
 
 	if (mode == ADD_P_STASH)

@@ -1612,6 +1614,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	    parse_diff(&s, ps) < 0) {
 		strbuf_release(&s.plain);
 		strbuf_release(&s.colored);
+		sigchain_pop(SIGPIPE);
 		return -1;
 	}

@@ -1630,5 +1633,6 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	strbuf_release(&s.buf);
 	strbuf_release(&s.plain);
 	strbuf_release(&s.colored);
+	sigchain_pop(SIGPIPE);
 	return 0;
 }

-- 
gitgitgadget

Re: [PATCH v3 01/10] built-in add -i/-p: treat SIGPIPE as EOF

From: Jeff King <hidden>
Date: 2020-01-13 18:33:16

On Mon, Jan 13, 2020 at 06:04:17PM +0100, SZEDER Gábor wrote:

After looking into it, the issue seems to be sending data to the
broken diffFilter process.  So in that test the diff is "filtered"
through 'echo too-short', which exits real fast, and doesn't read its
standard input at all (well, apart from e.g. the usual kernel
buffering that might happen on a pipe between the two processes).
Making sure that the diffFilter process reads all the data before
exiting, i.e. changing it to:

  test_config interactive.diffFilter "cat >/dev/null ; echo too-short" &&

made the test reliable, with over 2000 --stress repetitions, and that
with only a single "y" on 'git add's stdin.

Yeah, I agree the test should be changed. What you wrote above was my
first thought, too, but I think "sed 1d" is actually a more realistic
test (and is shorter and one fewer process).

Now, merely tweaking the test is clearly insufficient, because we not
only want the test to be realiable, but we want 'git add' to die
gracefully when users out there mess up their configuration.

I also agree that it would be nice to deal with this for real-world
cases. I suspect it's not something that would come up a lot, though.

Ignoring SIGPIPE can surely accomplish that, but I'm not sure about
the scope.  I mean your patch seems to ignore SIGPIPE basically for
almost the whole 'git add -(i|p)' process, but perhaps it should be
limited only to the surroundings of the pipe_command() call running
the diffFilter, and be done as part of the next patch adding the 'if
(diff_filter)' block.

The scope there is probably OK in practice. In my opinion SIGPIPE is
usually _not_ what the behavior we want. If we're carefully checking our
write() return values, then we'd get EPIPE in such an instance and
behave appropriately. And if we're not checking our write() return
values, that's generally a bug that ought to be fixed.

The big exception is when we are writing copious output to stdout (or
the pager) via printf() or similar, and want to die rather than continue
writing output nobody will see. But I don't think git-add really counts
as generating a lot of output, where EPIPE could prevent us from doing
useless work (unlike, say, git-log).

Furthermore, I'm worried that by simply ignoring SIGPIPE we might just
ignore a more fundamental issue in pipe_command(): shouldn't that
function be smart enough not to write() to a fd that has no one on the
other side to read it in the first place?!

Maybe. As you noted below, checking for POLLERR is racy. Seeing that we
"can" write to an fd and doing it to discover what write() returns
(whether error or not) doesn't seem like the worst strategy. If the
caller cares about pipe death, then it needs to be handling SIGPIPE
anyway.

I really wish there was a way to set a handler for SIGPIPE that tells
_which_ descriptor caused it. Because I think logic like "die if it was
fd 1, ignore and let write() return EPIPE otherwise" is the behavior
we'd like. But I don't think there's a portable way to do so.

I've been tempted to say that we should just ignore SIGPIPE everywhere,
and convert even copious-output programs like git-log to just check for
errors (they could probably even just check ferror(stdout) for each
commit we output, if we didn't want to touch every printf call).

-Peff

Re: [PATCH v3 01/10] built-in add -i/-p: treat SIGPIPE as EOF

From: Johannes Schindelin <hidden>
Date: 2020-01-14 12:47:57

Hi Gábor,

On Mon, 13 Jan 2020, SZEDER Gábor wrote:

On Mon, Jan 13, 2020 at 08:29:22AM +0000, Johannes Schindelin via GitGitGadget wrote:

quoted

From: Johannes Schindelin <redacted>

As noticed by Gábor Szeder, if we want to run `git add -p` with
redirected input through `test_must_fail` in the test suite, we must
expect that a SIGPIPE can happen due to `stdin` coming to its end.

I don't think this issue is related to the redirected input: I
modified that flaky test to send "unlimited" data to 'git add's stdin,
i.e.:

  /usr/bin/yes | test_must_fail force_color git add -p

and the test with --stress still failed with SIGPIPE all the same and
just as fast.

After looking into it, the issue seems to be sending data to the
broken diffFilter process.

Ouch. Thank you for investigating. For my education, how did you debug
this? I could not find a way to identify *what* caused that SIGPIPE...

So in that test the diff is "filtered" through 'echo too-short', which
exits real fast, and doesn't read its standard input at all (well, apart
from e.g. the usual kernel buffering that might happen on a pipe between
the two processes). Making sure that the diffFilter process reads all
the data before exiting, i.e. changing it to:

  test_config interactive.diffFilter "cat >/dev/null ; echo too-short" &&

made the test reliable, with over 2000 --stress repetitions, and that
with only a single "y" on 'git add's stdin.

Ah, my diff filter simply ignores the `stdin`... That's easy enough to
fix, and since real-world diff filters probably won't just blatantly
ignore the input, I think it is legitimate to change the test.

Now, merely tweaking the test is clearly insufficient, because we not
only want the test to be realiable, but we want 'git add' to die
gracefully when users out there mess up their configuration.

I think it is sufficient to tweak the test, but I agree that a better
error message might be good when users out there mess up their
configuration.

Ignoring SIGPIPE can surely accomplish that, but I'm not sure about
the scope.  I mean your patch seems to ignore SIGPIPE basically for
almost the whole 'git add -(i|p)' process, but perhaps it should be
limited only to the surroundings of the pipe_command() call running
the diffFilter, and be done as part of the next patch adding the 'if
(diff_filter)' block.

Right. Very heavy-handed, and probably inviting unwanted side effects.

quoted hunk

Furthermore, I'm worried that by simply ignoring SIGPIPE we might just
ignore a more fundamental issue in pipe_command(): shouldn't that
function be smart enough not to write() to a fd that has no one on the
other side to read it in the first place?!

So, when the diffFilter process exits unexpectedly early, then the
poll() call in pipe_command() -> pump_io() -> pump_io_round() returns
with success and usually sets 'revents' for the child process' stdin
to 12 (i.e. 'POLLOUT | POLLERR'; gah, how I hate unnamed constants :).
Unfortunately, at that point we don't take any special action on
POLLERR, but call xwrite() to try to write to the dead fd anyway,
which then promptly triggers SIGPIPE.  (This is what usually happens
when stepping through the statements of those functions in a debugger,
and the diffFilter process has all the time in the world to exit.)

We could handle POLLERR with a patch like this:

  --- >8 ---

Subject: run-command: handle POLLERR in pump_io_round() to reduce risk of SIGPIPE

diff --git a/run-command.c b/run-command.c
index 3449db319b..57093f0acc 100644
--- a/run-command.c
+++ b/run-command.c

@@ -1416,25 +1416,31 @@ static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
 	if (poll(pfd, pollsize, -1) < 0) {
 		if (errno == EINTR)
 			return 1;
 		die_errno("poll failed");
 	}

 	for (i = 0; i < nr; i++) {
 		struct io_pump *io = &slots[i];

 		if (io->fd < 0)
 			continue;

-		if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
+		if (io->pfd->revents & POLLERR) {
+			io->error = ECONNRESET;  /* What should we report to the caller? */
+			close(io->fd);
+			io->fd = -1;
+			continue;
+		}
+		if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLNVAL)))
 			continue;

 		if (io->type == POLLOUT) {
 			ssize_t len = xwrite(io->fd,
 					     io->u.out.buf, io->u.out.len);
 			if (len < 0) {
 				io->error = errno;
 				close(io->fd);
 				io->fd = -1;
 			} else {
 				io->u.out.buf += len;
 				io->u.out.len -= len;

  --- >8 ---

Unfortunately #1, this changes the error 'git add -p' dies with from:

  error: mismatched output from interactive.diffFilter

to:

  error: failed to run 'echo too-short'

It might affect other commands as well, but FWIW the test suite
doesn't catch any.

Hmm. My first impression is that the error message could be a bit better,
but that it is probably a good thing to have. It would have helped _me_
understand the issue at hand.

quoted hunk

Unfortunately #2, the above patch doesn't completely eliminates the
SIGPIPE, but only (greatly) reduces its probability.  It is possible
that:

  - poll() returns with success and indicating a writable fd without
    any error, i.e. 'revents = 4'.

  - the bogus diffFilter exits, closing its stdin.

  - 'git add' attempts to xwrite() to the now closed fd, and triggers
    a SIGPIPE right away.

This happens much rarer, 'GIT_TEST_ADD_I_USE_BUILTIN=1
./t3701-add-interactive.sh -r 39,49 --stress-jobs=<4*nr-of-cores>
--stress' tends to take over 200 repetitions.  The patch below
reproduces it fairly reliably by adding two strategically-placed
sleep()s, with a bit of extra debug output:

  --- >8 ---

diff --git a/add-patch.c b/add-patch.c
index d8dafa8168..0fd017bbd3 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -421,6 +421,7 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 			filter_cp.git_cmd = 0;
 			filter_cp.use_shell = 1;
 			strbuf_reset(&s->buf);
+			fprintf(stderr, "about to run diffFilter\n");
 			if (pipe_command(&filter_cp,
 					 colored->buf, colored->len,
 					 &s->buf, colored->len,

diff --git a/run-command.c b/run-command.c
index 57093f0acc..49ae88a922 100644
--- a/run-command.c
+++ b/run-command.c

@@ -1419,6 +1419,7 @@ static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
 		die_errno("poll failed");
 	}

+	sleep(2);
 	for (i = 0; i < nr; i++) {
 		struct io_pump *io = &slots[i];

@@ -1435,8 +1436,11 @@ static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
 			continue;

 		if (io->type == POLLOUT) {
-			ssize_t len = xwrite(io->fd,
+			ssize_t len;
+			fprintf(stderr, "attempting to xwrite() %lu bytes to a fd with revents flags 0x%hx\n", io->u.out.len, io->pfd->revents);
+			len = xwrite(io->fd,
 					     io->u.out.buf, io->u.out.len);
+			fprintf(stderr, "after xwrite()\n");
 			if (len < 0) {
 				io->error = errno;
 				close(io->fd);

diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index 12ee321707..acffc9af37 100755
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh

@@ -561,7 +561,7 @@ test_expect_success 'detect bogus diffFilter output' '
 	git reset --hard &&

 	echo content >test &&
-	test_config interactive.diffFilter "echo too-short" &&
+	test_config interactive.diffFilter "sleep 1 ; echo too-short" &&
 	printf y >y &&
 	test_must_fail force_color git add -p <y
 '

  --- >8 ---

and 'GIT_TEST_ADD_I_USE_BUILTIN=1 ./t3701-add-interactive.sh -r 39,49'
fails with:

  + test_must_fail force_color git add -p
  about to run diffFilter
  attempting to xwrite() 224 bytes to a fd with revents flags 0x4
  test_must_fail: died by signal 13: force_color git add -p

I don't understand why we get SIGPIPE right away instead of some error
that we can act upon (ECONNRESET?).

Isn't it buffered?

In any case, I would take the above-mentioned patch, even if it makes it
"only" less likely to hit `SIGPIPE`.

FWIW, it fails the same way not only on my box, but on Travis CI's Linux
and OSX images as well.

  https://travis-ci.org/szeder/git/jobs/636446843#L2937


Cc'ing Peff for all things SIGPIPE :) who also happens to be the
author of both pipe_command() and that now flaky test.

I'll go with Peff's suggestion to use `sed 1d` instead of `echo
too-short`.

Thanks,
Dscho

[PATCH v4 00/10] built-in add -p: add support for the same config settings as the Perl version

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:00

This is the final leg of the journey to a fully built-in git add: the git
add -i and git add -p modes were re-implemented in C, but they lacked
support for a couple of config settings.

The one that sticks out most is the interactive.singleKey setting: it was
particularly hard to get to work, especially on Windows.

It also seems to be the setting that is incomplete already in the Perl
version of the interactive add command: while the name of the config setting
suggests that it applies to all of the interactive add, including the main
loop of git add --interactive and to the file selections in that command, it
does not. Only the git add --patch mode respects that setting.

As it is outside the purpose of the conversion of git-add--interactive.perl 
to C, we will leave that loose end for some future date.

Changes since v3:

 * Reverted that heavy-handed SIGPIPE handling.
 * Instead, changed the diffFilter test case to process the standard input
   instead of ignoring it.

(The range diff between v2 and v4 actually only shows the new patch 1/10
"t3701: adjust difffilter test".)

Changes since v2:

 * Fixed the SIGPIPE issue pointed out by Gábor Szeder.

Changes since v1:

 * Fixed the commit message where a copy/paste fail made it talk about
   another GIT_TEST_* variable than the GIT_TEST_ADD_I_USE_BUILTIN one.

Johannes Schindelin (10):
  t3701: adjust difffilter test
  built-in add -p: support interactive.diffFilter
  built-in add -p: handle diff.algorithm
  terminal: make the code of disable_echo() reusable
  terminal: accommodate Git for Windows' default terminal
  terminal: add a new function to read a single keystroke
  built-in add -p: respect the `interactive.singlekey` config setting
  built-in add -p: handle Escape sequences in interactive.singlekey mode
  built-in add -p: handle Escape sequences more efficiently
  ci: include the built-in `git add -i` in the `linux-gcc` job

 add-interactive.c          |  19 +++
 add-interactive.h          |   4 +
 add-patch.c                |  57 ++++++++-
 ci/run-build-and-tests.sh  |   1 +
 compat/terminal.c          | 249 ++++++++++++++++++++++++++++++++++++-
 compat/terminal.h          |   3 +
 t/t3701-add-interactive.sh |   2 +-
 7 files changed, 326 insertions(+), 9 deletions(-)


base-commit: c480eeb574e649a19f27dc09a994e45f9b2c2622
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-175%2Fdscho%2Fadd-p-in-c-config-settings-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-175/dscho/add-p-in-c-config-settings-v4
Pull-Request: https://github.com/gitgitgadget/git/pull/175

Range-diff vs v3:

  1:  5e258a8d2b <  -:  ---------- built-in add -i/-p: treat SIGPIPE as EOF
  -:  ---------- >  1:  e12df77e8a t3701: adjust difffilter test
  2:  2a5951ecfe !  2:  413a87bd79 built-in add -p: support interactive.diffFilter
     @@ -35,9 +35,9 @@
       	strbuf_release(&header);
       	prefix_item_list_clear(&commands);
      +	clear_add_i_state(&s);
     - 	sigchain_pop(SIGPIPE);
       
       	return res;
     + }
      
       diff --git a/add-interactive.h b/add-interactive.h
       --- a/add-interactive.h
     @@ -123,14 +123,13 @@
       		strbuf_release(&s.plain);
       		strbuf_release(&s.colored);
      +		clear_add_i_state(&s.s);
     - 		sigchain_pop(SIGPIPE);
       		return -1;
       	}
     + 
      @@
       	strbuf_release(&s.buf);
       	strbuf_release(&s.plain);
       	strbuf_release(&s.colored);
      +	clear_add_i_state(&s.s);
     - 	sigchain_pop(SIGPIPE);
       	return 0;
       }
  3:  a2bce01818 =  3:  062c624547 built-in add -p: handle diff.algorithm
  4:  be40a37c0c =  4:  09a8946303 terminal: make the code of disable_echo() reusable
  5:  233f23791c =  5:  a81304cb76 terminal: accommodate Git for Windows' default terminal
  6:  74593b5115 =  6:  8d9c703f3b terminal: add a new function to read a single keystroke
  7:  197fe1e14a !  7:  8ed4487ae4 built-in add -p: respect the `interactive.singlekey` config setting
     @@ -48,9 +48,9 @@
       --- a/add-patch.c
       +++ b/add-patch.c
      @@
     + #include "pathspec.h"
       #include "color.h"
       #include "diff.h"
     - #include "sigchain.h"
      +#include "compat/terminal.h"
       
       enum prompt_mode_type {
  8:  9ab381d539 =  8:  cdc609f8fa built-in add -p: handle Escape sequences in interactive.singlekey mode
  9:  bdb6268b8b =  9:  80b0f2528d built-in add -p: handle Escape sequences more efficiently
 10:  c4195969a6 = 10:  7ab7ec62d0 ci: include the built-in `git add -i` in the `linux-gcc` job

-- 
gitgitgadget

[PATCH v4 01/10] t3701: adjust difffilter test

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:00

From: Johannes Schindelin <redacted>

In 42f7d45428e (add--interactive: detect bogus diffFilter output,
2018-03-03), we added a test case that verifies that the diffFilter
feature complains appropriately when the output is too short.

In preparation for the upcoming change where the built-in `add -p` is
taught to respect that setting, let's adjust that test a little. The
problem is that `echo too-short` is configured as diffFilter, and it
does not read the `stdin`. When calling it through `pipe_command()`, it
is therefore possible that we try to feed the `diff` to it while it is
no longer listening, and we receive a `SIGPIPE`.

The Perl code apparently handles this in a way similar to an
end-of-file, but taking a step back, we realize that a diffFilter that
does not even _look_ at its standard input is very unrealistic. The
entire point of this feature is to transform the diff, not to ignore it
altogether.

So let's modify the test case to reflect that insight: instead of
printing some bogus text, let's use a diffFilter that deletes the first
line of the diff instead.

This still tests for the same thing, but it does not confuse the
built-in `add -p` with that `SIGPIPE`.

Helped-by: SZEDER Gábor [off-list ref]
Helped-by: Jeff King [off-list ref]
Signed-off-by: Johannes Schindelin <redacted>
---
 t/t3701-add-interactive.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index 12ee321707..ac43f835a5 100755
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh

@@ -561,7 +561,7 @@ test_expect_success 'detect bogus diffFilter output' '
 	git reset --hard &&
 
 	echo content >test &&
-	test_config interactive.diffFilter "echo too-short" &&
+	test_config interactive.diffFilter "sed 1d" &&
 	printf y >y &&
 	test_must_fail force_color git add -p <y
 '

-- 
gitgitgadget

[PATCH v4 02/10] built-in add -p: support interactive.diffFilter

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:02

From: Johannes Schindelin <redacted>

The Perl version supports post-processing the colored diff (that is
generated in addition to the uncolored diff, intended to offer a
prettier user experience) by a command configured via that config
setting, and now the built-in version does that, too.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 12 ++++++++++++
 add-interactive.h |  3 +++
 add-patch.c       | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index a5bb14f2f4..1786ea29c4 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -52,6 +52,17 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 		diff_get_color(s->use_color, DIFF_FILE_OLD));
 	init_color(r, s, "new", s->file_new_color,
 		diff_get_color(s->use_color, DIFF_FILE_NEW));
+
+	FREE_AND_NULL(s->interactive_diff_filter);
+	git_config_get_string("interactive.difffilter",
+			      &s->interactive_diff_filter);
+}
+
+void clear_add_i_state(struct add_i_state *s)
+{
+	FREE_AND_NULL(s->interactive_diff_filter);
+	memset(s, 0, sizeof(*s));
+	s->use_color = -1;
 }
 
 /*

@@ -1149,6 +1160,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	strbuf_release(&print_file_item_data.worktree);
 	strbuf_release(&header);
 	prefix_item_list_clear(&commands);
+	clear_add_i_state(&s);
 
 	return res;
 }

diff --git a/add-interactive.h b/add-interactive.h
index b2f23479c5..46c73867ad 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -15,9 +15,12 @@ struct add_i_state {
 	char context_color[COLOR_MAXLEN];
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
+
+	char *interactive_diff_filter;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);
+void clear_add_i_state(struct add_i_state *s);
 
 struct repository;
 struct pathspec;

diff --git a/add-patch.c b/add-patch.c
index 46c6c183d5..78bde41df0 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -398,6 +398,7 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 
 	if (want_color_fd(1, -1)) {
 		struct child_process colored_cp = CHILD_PROCESS_INIT;
+		const char *diff_filter = s->s.interactive_diff_filter;
 
 		setup_child_process(s, &colored_cp, NULL);
 		xsnprintf((char *)args.argv[color_arg_index], 8, "--color");

@@ -407,6 +408,24 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		argv_array_clear(&args);
 		if (res)
 			return error(_("could not parse colored diff"));
+
+		if (diff_filter) {
+			struct child_process filter_cp = CHILD_PROCESS_INIT;
+
+			setup_child_process(s, &filter_cp,
+					    diff_filter, NULL);
+			filter_cp.git_cmd = 0;
+			filter_cp.use_shell = 1;
+			strbuf_reset(&s->buf);
+			if (pipe_command(&filter_cp,
+					 colored->buf, colored->len,
+					 &s->buf, colored->len,
+					 NULL, 0) < 0)
+				return error(_("failed to run '%s'"),
+					     diff_filter);
+			strbuf_swap(colored, &s->buf);
+		}
+
 		strbuf_complete_line(colored);
 		colored_p = colored->buf;
 		colored_pend = colored_p + colored->len;

@@ -531,6 +550,9 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 						   colored_pend - colored_p);
 			if (colored_eol)
 				colored_p = colored_eol + 1;
+			else if (p != pend)
+				/* colored shorter than non-colored? */
+				goto mismatched_output;
 			else
 				colored_p = colored_pend;

@@ -555,6 +577,15 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 		 */
 		hunk->splittable_into++;
 
+	/* non-colored shorter than colored? */
+	if (colored_p != colored_pend) {
+mismatched_output:
+		error(_("mismatched output from interactive.diffFilter"));
+		advise(_("Your filter must maintain a one-to-one correspondence\n"
+			 "between its input and output lines."));
+		return -1;
+	}
+
 	return 0;
 }

@@ -1612,6 +1643,7 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	    parse_diff(&s, ps) < 0) {
 		strbuf_release(&s.plain);
 		strbuf_release(&s.colored);
+		clear_add_i_state(&s.s);
 		return -1;
 	}

@@ -1630,5 +1662,6 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
 	strbuf_release(&s.buf);
 	strbuf_release(&s.plain);
 	strbuf_release(&s.colored);
+	clear_add_i_state(&s.s);
 	return 0;
 }

-- 
gitgitgadget

[PATCH v4 05/10] terminal: accommodate Git for Windows' default terminal

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:05

From: Johannes Schindelin <redacted>

Git for Windows' Git Bash runs in MinTTY by default, which does not have
a Win32 Console instance, but uses MSYS2 pseudo terminals instead.

This is a problem, as Git for Windows does not want to use the MSYS2
emulation layer for Git itself, and therefore has no direct way to
interact with that pseudo terminal.

As a workaround, use the `stty` utility (which is included in Git for
Windows, and which *is* an MSYS2 program, so it knows how to deal with
the pseudo terminal).

Note: If Git runs in a regular CMD or PowerShell window, there *is* a
regular Win32 Console to work with. This is not a problem for the MSYS2
`stty`: it copes with this scenario just fine.

Also note that we introduce support for more bits than would be
necessary for a mere `disable_echo()` here, in preparation for the
upcoming `enable_non_canonical()` function.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/compat/terminal.c b/compat/terminal.c
index 1fb40b3a0a..16e9949da1 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -2,6 +2,8 @@
 #include "compat/terminal.h"
 #include "sigchain.h"
 #include "strbuf.h"
+#include "run-command.h"
+#include "string-list.h"
 
 #if defined(HAVE_DEV_TTY) || defined(GIT_WINDOWS_NATIVE)

@@ -64,11 +66,28 @@ static int disable_echo(void)
 #define OUTPUT_PATH "CONOUT$"
 #define FORCE_TEXT "t"
 
+static int use_stty = 1;
+static struct string_list stty_restore = STRING_LIST_INIT_DUP;
 static HANDLE hconin = INVALID_HANDLE_VALUE;
 static DWORD cmode;
 
 static void restore_term(void)
 {
+	if (use_stty) {
+		int i;
+		struct child_process cp = CHILD_PROCESS_INIT;
+
+		if (stty_restore.nr == 0)
+			return;
+
+		argv_array_push(&cp.args, "stty");
+		for (i = 0; i < stty_restore.nr; i++)
+			argv_array_push(&cp.args, stty_restore.items[i].string);
+		run_command(&cp);
+		string_list_clear(&stty_restore, 0);
+		return;
+	}
+
 	if (hconin == INVALID_HANDLE_VALUE)
 		return;

@@ -79,6 +98,37 @@ static void restore_term(void)
 
 static int disable_bits(DWORD bits)
 {
+	if (use_stty) {
+		struct child_process cp = CHILD_PROCESS_INIT;
+
+		argv_array_push(&cp.args, "stty");
+
+		if (bits & ENABLE_LINE_INPUT) {
+			string_list_append(&stty_restore, "icanon");
+			argv_array_push(&cp.args, "-icanon");
+		}
+
+		if (bits & ENABLE_ECHO_INPUT) {
+			string_list_append(&stty_restore, "echo");
+			argv_array_push(&cp.args, "-echo");
+		}
+
+		if (bits & ENABLE_PROCESSED_INPUT) {
+			string_list_append(&stty_restore, "-ignbrk");
+			string_list_append(&stty_restore, "intr");
+			string_list_append(&stty_restore, "^c");
+			argv_array_push(&cp.args, "ignbrk");
+			argv_array_push(&cp.args, "intr");
+			argv_array_push(&cp.args, "");
+		}
+
+		if (run_command(&cp) == 0)
+			return 0;
+
+		/* `stty` could not be executed; access the Console directly */
+		use_stty = 0;
+	}
+
 	hconin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
 	    FILE_SHARE_READ, NULL, OPEN_EXISTING,
 	    FILE_ATTRIBUTE_NORMAL, NULL);

-- 
gitgitgadget

[PATCH v4 08/10] built-in add -p: handle Escape sequences in interactive.singlekey mode

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:07

From: Johannes Schindelin <redacted>

This recapitulates part of b5cc003253c8 (add -i: ignore terminal escape
sequences, 2011-05-17):

    add -i: ignore terminal escape sequences

    On the author's terminal, the up-arrow input sequence is ^[[A, and
    thus fat-fingering an up-arrow into 'git checkout -p' is quite
    dangerous: git-add--interactive.perl will ignore the ^[ and [
    characters and happily treat A as "discard everything".

    As a band-aid fix, use Term::Cap to get all terminal capabilities.
    Then use the heuristic that any capability value that starts with ^[
    (i.e., \e in perl) must be a key input sequence.  Finally, given an
    input that starts with ^[, read more characters until we have read a
    full escape sequence, then return that to the caller.  We use a
    timeout of 0.5 seconds on the subsequent reads to avoid getting stuck
    if the user actually input a lone ^[.

    Since none of the currently recognized keys start with ^[, the net
    result is that the sequence as a whole will be ignored and the help
    displayed.

Note that we leave part for later which uses "Term::Cap to get all
terminal capabilities", for several reasons:

1. it is actually not really necessary, as the timeout of 0.5 seconds
   should be plenty sufficient to catch Escape sequences,

2. it is cleaner to keep the change to special-case Escape sequences
   separate from the change that reads all terminal capabilities to
   speed things up, and

3. in practice, relying on the terminal capabilities is a bit overrated,
   as the information could be incomplete, or plain wrong. For example,
   in this developer's tmux sessions, the terminal capabilities claim
   that the "cursor up" sequence is ^[M, but the actual sequence
   produced by the "cursor up" key is ^[[A.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index 1b2564042a..b7f58d1781 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -161,6 +161,37 @@ static int enable_non_canonical(void)
 	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
 }
 
+/*
+ * Override `getchar()`, as the default implementation does not use
+ * `ReadFile()`.
+ *
+ * This poses a problem when we want to see whether the standard
+ * input has more characters, as the default of Git for Windows is to start the
+ * Bash in a MinTTY, which uses a named pipe to emulate a pty, in which case
+ * our `poll()` emulation calls `PeekNamedPipe()`, which seems to require
+ * `ReadFile()` to be called first to work properly (it only reports 0
+ * available bytes, otherwise).
+ *
+ * So let's just override `getchar()` with a version backed by `ReadFile()` and
+ * go our merry ways from here.
+ */
+static int mingw_getchar(void)
+{
+	DWORD read = 0;
+	unsigned char ch;
+
+	if (!ReadFile(GetStdHandle(STD_INPUT_HANDLE), &ch, 1, &read, NULL))
+		return EOF;
+
+	if (!read) {
+		error("Unexpected 0 read");
+		return EOF;
+	}
+
+	return ch;
+}
+#define getchar mingw_getchar
+
 #endif
 
 #ifndef FORCE_TEXT

@@ -228,8 +259,31 @@ int read_key_without_echo(struct strbuf *buf)
 		restore_term();
 		return EOF;
 	}
-
 	strbuf_addch(buf, ch);
+
+	if (ch == '\033' /* ESC */) {
+		/*
+		 * We are most likely looking at an Escape sequence. Let's try
+		 * to read more bytes, waiting at most half a second, assuming
+		 * that the sequence is complete if we did not receive any byte
+		 * within that time.
+		 *
+		 * Start by replacing the Escape byte with ^[ */
+		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
+
+		for (;;) {
+			struct pollfd pfd = { .fd = 0, .events = POLLIN };
+
+			if (poll(&pfd, 1, 500) < 1)
+				break;
+
+			ch = getchar();
+			if (ch == EOF)
+				return 0;
+			strbuf_addch(buf, ch);
+		}
+	}
+
 	restore_term();
 	return 0;
 }

-- 
gitgitgadget

[PATCH v4 10/10] ci: include the built-in `git add -i` in the `linux-gcc` job

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:08

From: Johannes Schindelin <redacted>

This job runs the test suite twice, once in regular mode, and once with
a whole slew of `GIT_TEST_*` variables set.

Now that the built-in version of `git add --interactive` is
feature-complete, let's also throw `GIT_TEST_ADD_I_USE_BUILTIN` into
that fray.

Signed-off-by: Johannes Schindelin <redacted>
---
 ci/run-build-and-tests.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index ff0ef7f08e..4df54c4efe 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh

@@ -20,6 +20,7 @@ linux-gcc)
 	export GIT_TEST_OE_DELTA_SIZE=5
 	export GIT_TEST_COMMIT_GRAPH=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
+	export GIT_TEST_ADD_I_USE_BUILTIN=1
 	make test
 	;;
 linux-gcc-4.8)

-- 
gitgitgadget

[PATCH v4 07/10] built-in add -p: respect the `interactive.singlekey` config setting

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:09

From: Johannes Schindelin <redacted>

The Perl version of `git add -p` supports this config setting to allow
users to input commands via single characters (as opposed to having to
press the <Enter> key afterwards).

This is an opt-in feature because it requires Perl packages
(Term::ReadKey and Term::Cap, where it tries to handle an absence of the
latter package gracefully) to work. Note that at least on Ubuntu, that
Perl package is not installed by default (it needs to be installed via
`sudo apt-get install libterm-readkey-perl`), so this feature is
probably not used a whole lot.

In C, we obviously do not have these packages available, but we just
introduced `read_single_keystroke()` that is similar to what
Term::ReadKey provides, and we use that here.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c |  2 ++
 add-interactive.h |  1 +
 add-patch.c       | 21 +++++++++++++++++----
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index 9e4bcb382c..39c3896494 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -60,6 +60,8 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	FREE_AND_NULL(s->interactive_diff_algorithm);
 	git_config_get_string("diff.algorithm",
 			      &s->interactive_diff_algorithm);
+
+	git_config_get_bool("interactive.singlekey", &s->use_single_key);
 }
 
 void clear_add_i_state(struct add_i_state *s)

diff --git a/add-interactive.h b/add-interactive.h
index 923efaf527..693f125e8e 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -16,6 +16,7 @@ struct add_i_state {
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
 
+	int use_single_key;
 	char *interactive_diff_filter, *interactive_diff_algorithm;
 };

diff --git a/add-patch.c b/add-patch.c
index 8f2ee8688b..d8dafa8168 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -6,6 +6,7 @@
 #include "pathspec.h"
 #include "color.h"
 #include "diff.h"
+#include "compat/terminal.h"
 
 enum prompt_mode_type {
 	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK,

@@ -1149,14 +1150,27 @@ static int run_apply_check(struct add_p_state *s,
 	return 0;
 }
 
+static int read_single_character(struct add_p_state *s)
+{
+	if (s->s.use_single_key) {
+		int res = read_key_without_echo(&s->answer);
+		printf("%s\n", res == EOF ? "" : s->answer.buf);
+		return res;
+	}
+
+	if (strbuf_getline(&s->answer, stdin) == EOF)
+		return EOF;
+	strbuf_trim_trailing_newline(&s->answer);
+	return 0;
+}
+
 static int prompt_yesno(struct add_p_state *s, const char *prompt)
 {
 	for (;;) {
 		color_fprintf(stdout, s->s.prompt_color, "%s", _(prompt));
 		fflush(stdout);
-		if (strbuf_getline(&s->answer, stdin) == EOF)
+		if (read_single_character(s) == EOF)
 			return -1;
-		strbuf_trim_trailing_newline(&s->answer);
 		switch (tolower(s->answer.buf[0])) {
 		case 'n': return 0;
 		case 'y': return 1;

@@ -1396,9 +1410,8 @@ static int patch_update_file(struct add_p_state *s,
 			      _(s->mode->prompt_mode[prompt_mode_type]),
 			      s->buf.buf);
 		fflush(stdout);
-		if (strbuf_getline(&s->answer, stdin) == EOF)
+		if (read_single_character(s) == EOF)
 			break;
-		strbuf_trim_trailing_newline(&s->answer);
 
 		if (!s->answer.len)
 			continue;

-- 
gitgitgadget

[PATCH v4 03/10] built-in add -p: handle diff.algorithm

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:09

From: Johannes Schindelin <redacted>

The Perl version of `git add -p` reads the config setting
`diff.algorithm` and if set, uses it to generate the diff using the
specified algorithm.

This patch ports that functionality to the C version.

Note: just like `git-add--interactive.perl`, we do _not_ respect this
config setting in `git add -i`'s `diff` command, but _only_ in the
`patch` command.

Signed-off-by: Johannes Schindelin <redacted>
---
 add-interactive.c | 5 +++++
 add-interactive.h | 2 +-
 add-patch.c       | 3 +++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/add-interactive.c b/add-interactive.c
index 1786ea29c4..9e4bcb382c 100644
--- a/add-interactive.c
+++ b/add-interactive.c

@@ -56,11 +56,16 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	FREE_AND_NULL(s->interactive_diff_filter);
 	git_config_get_string("interactive.difffilter",
 			      &s->interactive_diff_filter);
+
+	FREE_AND_NULL(s->interactive_diff_algorithm);
+	git_config_get_string("diff.algorithm",
+			      &s->interactive_diff_algorithm);
 }
 
 void clear_add_i_state(struct add_i_state *s)
 {
 	FREE_AND_NULL(s->interactive_diff_filter);
+	FREE_AND_NULL(s->interactive_diff_algorithm);
 	memset(s, 0, sizeof(*s));
 	s->use_color = -1;
 }

diff --git a/add-interactive.h b/add-interactive.h
index 46c73867ad..923efaf527 100644
--- a/add-interactive.h
+++ b/add-interactive.h

@@ -16,7 +16,7 @@ struct add_i_state {
 	char file_old_color[COLOR_MAXLEN];
 	char file_new_color[COLOR_MAXLEN];
 
-	char *interactive_diff_filter;
+	char *interactive_diff_filter, *interactive_diff_algorithm;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);

diff --git a/add-patch.c b/add-patch.c
index 78bde41df0..8f2ee8688b 100644
--- a/add-patch.c
+++ b/add-patch.c

@@ -360,6 +360,7 @@ static int is_octal(const char *p, size_t len)
 static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 {
 	struct argv_array args = ARGV_ARRAY_INIT;
+	const char *diff_algorithm = s->s.interactive_diff_algorithm;
 	struct strbuf *plain = &s->plain, *colored = NULL;
 	struct child_process cp = CHILD_PROCESS_INIT;
 	char *p, *pend, *colored_p = NULL, *colored_pend = NULL, marker = '\0';

@@ -369,6 +370,8 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 	int res;
 
 	argv_array_pushv(&args, s->mode->diff_cmd);
+	if (diff_algorithm)
+		argv_array_pushf(&args, "--diff-algorithm=%s", diff_algorithm);
 	if (s->revision) {
 		struct object_id oid;
 		argv_array_push(&args,

-- 
gitgitgadget

[PATCH v4 06/10] terminal: add a new function to read a single keystroke

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:11

From: Johannes Schindelin <redacted>

Typically, input on the command-line is line-based. It is actually not
really easy to get single characters (or better put: keystrokes).

We provide two implementations here:

- One that handles `/dev/tty` based systems as well as native Windows.
  The former uses the `tcsetattr()` function to put the terminal into
  "raw mode", which allows us to read individual keystrokes, one by one.
  The latter uses `stty.exe` to do the same, falling back to direct
  Win32 Console access.

  Thanks to the refactoring leading up to this commit, this is a single
  function, with the platform-specific details hidden away in
  conditionally-compiled code blocks.

- A fall-back which simply punts and reads back an entire line.

Note that the function writes the keystroke into an `strbuf` rather than
a `char`, in preparation for reading Escape sequences (e.g. when the
user hit an arrow key). This is also required for UTF-8 sequences in
case the keystroke corresponds to a non-ASCII letter.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++
 compat/terminal.h |  3 +++
 2 files changed, 58 insertions(+)

diff --git a/compat/terminal.c b/compat/terminal.c
index 16e9949da1..1b2564042a 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -60,6 +60,11 @@ static int disable_echo(void)
 	return disable_bits(ECHO);
 }
 
+static int enable_non_canonical(void)
+{
+	return disable_bits(ICANON | ECHO);
+}
+
 #elif defined(GIT_WINDOWS_NATIVE)
 
 #define INPUT_PATH "CONIN$"

@@ -151,6 +156,10 @@ static int disable_echo(void)
 	return disable_bits(ENABLE_ECHO_INPUT);
 }
 
+static int enable_non_canonical(void)
+{
+	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
+}
 
 #endif

@@ -198,6 +207,33 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+int read_key_without_echo(struct strbuf *buf)
+{
+	static int warning_displayed;
+	int ch;
+
+	if (warning_displayed || enable_non_canonical() < 0) {
+		if (!warning_displayed) {
+			warning("reading single keystrokes not supported on "
+				"this platform; reading line instead");
+			warning_displayed = 1;
+		}
+
+		return strbuf_getline(buf, stdin);
+	}
+
+	strbuf_reset(buf);
+	ch = getchar();
+	if (ch == EOF) {
+		restore_term();
+		return EOF;
+	}
+
+	strbuf_addch(buf, ch);
+	restore_term();
+	return 0;
+}
+
 #else
 
 char *git_terminal_prompt(const char *prompt, int echo)

@@ -205,4 +241,23 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return getpass(prompt);
 }
 
+int read_key_without_echo(struct strbuf *buf)
+{
+	static int warning_displayed;
+	const char *res;
+
+	if (!warning_displayed) {
+		warning("reading single keystrokes not supported on this "
+			"platform; reading line instead");
+		warning_displayed = 1;
+	}
+
+	res = getpass("");
+	strbuf_reset(buf);
+	if (!res)
+		return EOF;
+	strbuf_addstr(buf, res);
+	return 0;
+}
+
 #endif

diff --git a/compat/terminal.h b/compat/terminal.h
index 97db7cd69d..a9d52b8464 100644
--- a/compat/terminal.h
+++ b/compat/terminal.h

@@ -3,4 +3,7 @@
 
 char *git_terminal_prompt(const char *prompt, int echo);
 
+/* Read a single keystroke, without echoing it to the terminal */
+int read_key_without_echo(struct strbuf *buf);
+
 #endif /* COMPAT_TERMINAL_H */

-- 
gitgitgadget

[PATCH v4 04/10] terminal: make the code of disable_echo() reusable

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:12

From: Johannes Schindelin <redacted>

We are about to introduce the function `enable_non_canonical()`, which
shares almost the complete code with `disable_echo()`.

Let's prepare for that, by refactoring out that shared code.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index fa13ee672d..1fb40b3a0a 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -32,7 +32,7 @@ static void restore_term(void)
 	term_fd = -1;
 }
 
-static int disable_echo(void)
+static int disable_bits(tcflag_t bits)
 {
 	struct termios t;

@@ -43,7 +43,7 @@ static int disable_echo(void)
 	old_term = t;
 	sigchain_push_common(restore_term_on_signal);
 
-	t.c_lflag &= ~ECHO;
+	t.c_lflag &= ~bits;
 	if (!tcsetattr(term_fd, TCSAFLUSH, &t))
 		return 0;

@@ -53,6 +53,11 @@ static int disable_echo(void)
 	return -1;
 }
 
+static int disable_echo(void)
+{
+	return disable_bits(ECHO);
+}
+
 #elif defined(GIT_WINDOWS_NATIVE)
 
 #define INPUT_PATH "CONIN$"

@@ -72,7 +77,7 @@ static void restore_term(void)
 	hconin = INVALID_HANDLE_VALUE;
 }
 
-static int disable_echo(void)
+static int disable_bits(DWORD bits)
 {
 	hconin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
 	    FILE_SHARE_READ, NULL, OPEN_EXISTING,

@@ -82,7 +87,7 @@ static int disable_echo(void)
 
 	GetConsoleMode(hconin, &cmode);
 	sigchain_push_common(restore_term_on_signal);
-	if (!SetConsoleMode(hconin, cmode & (~ENABLE_ECHO_INPUT))) {
+	if (!SetConsoleMode(hconin, cmode & ~bits)) {
 		CloseHandle(hconin);
 		hconin = INVALID_HANDLE_VALUE;
 		return -1;

@@ -91,6 +96,12 @@ static int disable_echo(void)
 	return 0;
 }
 
+static int disable_echo(void)
+{
+	return disable_bits(ENABLE_ECHO_INPUT);
+}
+
+
 #endif
 
 #ifndef FORCE_TEXT

-- 
gitgitgadget

[PATCH v4 09/10] built-in add -p: handle Escape sequences more efficiently

From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2020-01-14 18:44:14

From: Johannes Schindelin <redacted>

When `interactive.singlekey = true`, we react immediately to keystrokes,
even to Escape sequences (e.g. when pressing a cursor key).

The problem with Escape sequences is that we do not really know when
they are done, and as a heuristic we poll standard input for half a
second to make sure that we got all of it.

While waiting half a second is not asking for a whole lot, it can become
quite annoying over time, therefore with this patch, we read the
terminal capabilities (if available) and extract known Escape sequences
from there, then stop polling immediately when we detected that the user
pressed a key that generated such a known sequence.

This recapitulates the remaining part of b5cc003253c8 (add -i: ignore
terminal escape sequences, 2011-05-17).

Note: We do *not* query the terminal capabilities directly. That would
either require a lot of platform-specific code, or it would require
linking to a library such as ncurses.

Linking to a library in the built-ins is something we try very hard to
avoid (we even kicked the libcurl dependency to a non-built-in remote
helper, just to shave off a tiny fraction of a second from Git's startup
time). And the platform-specific code would be a maintenance nightmare.

Even worse: in Git for Windows' case, we would need to query MSYS2
pseudo terminals, which `git.exe` simply cannot do (because it is
intentionally *not* an MSYS2 program).

To address this, we simply spawn `infocmp -L -1` and parse its output
(which works even in Git for Windows, because that helper is included in
the end-user facing installations).

This is done only once, as in the Perl version, but it is done only when
the first Escape sequence is encountered, not upon startup of `git add
-i`; This saves on startup time, yet makes reacting to the first Escape
sequence slightly more sluggish. But it allows us to keep the
terminal-related code encapsulated in the `compat/terminal.c` file.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/terminal.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index b7f58d1781..35bca03d14 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c

@@ -4,6 +4,7 @@
 #include "strbuf.h"
 #include "run-command.h"
 #include "string-list.h"
+#include "hashmap.h"
 
 #if defined(HAVE_DEV_TTY) || defined(GIT_WINDOWS_NATIVE)

@@ -238,6 +239,71 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+/*
+ * The `is_known_escape_sequence()` function returns 1 if the passed string
+ * corresponds to an Escape sequence that the terminal capabilities contains.
+ *
+ * To avoid depending on ncurses or other platform-specific libraries, we rely
+ * on the presence of the `infocmp` executable to do the job for us (failing
+ * silently if the program is not available or refused to run).
+ */
+struct escape_sequence_entry {
+	struct hashmap_entry entry;
+	char sequence[FLEX_ARRAY];
+};
+
+static int sequence_entry_cmp(const void *hashmap_cmp_fn_data,
+			      const struct escape_sequence_entry *e1,
+			      const struct escape_sequence_entry *e2,
+			      const void *keydata)
+{
+	return strcmp(e1->sequence, keydata ? keydata : e2->sequence);
+}
+
+static int is_known_escape_sequence(const char *sequence)
+{
+	static struct hashmap sequences;
+	static int initialized;
+
+	if (!initialized) {
+		struct child_process cp = CHILD_PROCESS_INIT;
+		struct strbuf buf = STRBUF_INIT;
+		char *p, *eol;
+
+		hashmap_init(&sequences, (hashmap_cmp_fn)sequence_entry_cmp,
+			     NULL, 0);
+
+		argv_array_pushl(&cp.args, "infocmp", "-L", "-1", NULL);
+		if (pipe_command(&cp, NULL, 0, &buf, 0, NULL, 0))
+			strbuf_setlen(&buf, 0);
+
+		for (eol = p = buf.buf; *p; p = eol + 1) {
+			p = strchr(p, '=');
+			if (!p)
+				break;
+			p++;
+			eol = strchrnul(p, '\n');
+
+			if (starts_with(p, "\\E")) {
+				char *comma = memchr(p, ',', eol - p);
+				struct escape_sequence_entry *e;
+
+				p[0] = '^';
+				p[1] = '[';
+				FLEX_ALLOC_MEM(e, sequence, p, comma - p);
+				hashmap_entry_init(&e->entry,
+						   strhash(e->sequence));
+				hashmap_add(&sequences, &e->entry);
+			}
+			if (!*eol)
+				break;
+		}
+		initialized = 1;
+	}
+
+	return !!hashmap_get_from_hash(&sequences, strhash(sequence), sequence);
+}
+
 int read_key_without_echo(struct strbuf *buf)
 {
 	static int warning_displayed;

@@ -271,7 +337,12 @@ int read_key_without_echo(struct strbuf *buf)
 		 * Start by replacing the Escape byte with ^[ */
 		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
 
-		for (;;) {
+		/*
+		 * Query the terminal capabilities once about all the Escape
+		 * sequences it knows about, so that we can avoid waiting for
+		 * half a second when we know that the sequence is complete.
+		 */
+		while (!is_known_escape_sequence(buf->buf)) {
 			struct pollfd pfd = { .fd = 0, .events = POLLIN };
 
 			if (poll(&pfd, 1, 500) < 1)

-- 
gitgitgadget

Re: [PATCH v3 01/10] built-in add -i/-p: treat SIGPIPE as EOF

From: SZEDER Gábor <hidden>
Date: 2020-01-17 14:32:45

On Mon, Jan 13, 2020 at 06:04:17PM +0100, SZEDER Gábor wrote:

and 'GIT_TEST_ADD_I_USE_BUILTIN=1 ./t3701-add-interactive.sh -r 39,49'
fails with:

  + test_must_fail force_color git add -p
  about to run diffFilter
  attempting to xwrite() 224 bytes to a fd with revents flags 0x4
  test_must_fail: died by signal 13: force_color git add -p

I don't understand why we get SIGPIPE right away instead of some error
that we can act upon (ECONNRESET?).

Doh', because it's a pipe, not a socket, that's why.  pipe(7):

  "If all file descriptors referring to the read end of a pipe have
   been closed, then a write(2) will cause a SIGPIPE signal to be
   generated for the calling process."

So ECONNRESET is definitely not the right error to set on POLLERR,
though I'm still not sure what the right one would be (perhaps
EPIPE?).

Re: [PATCH v3 01/10] built-in add -i/-p: treat SIGPIPE as EOF

From: Jeff King <hidden>
Date: 2020-01-17 18:58:39

On Fri, Jan 17, 2020 at 03:32:36PM +0100, SZEDER Gábor wrote:

On Mon, Jan 13, 2020 at 06:04:17PM +0100, SZEDER Gábor wrote:

quoted

and 'GIT_TEST_ADD_I_USE_BUILTIN=1 ./t3701-add-interactive.sh -r 39,49'
fails with:

  + test_must_fail force_color git add -p
  about to run diffFilter
  attempting to xwrite() 224 bytes to a fd with revents flags 0x4
  test_must_fail: died by signal 13: force_color git add -p

I don't understand why we get SIGPIPE right away instead of some error
that we can act upon (ECONNRESET?).

Doh', because it's a pipe, not a socket, that's why.  pipe(7):

  "If all file descriptors referring to the read end of a pipe have
   been closed, then a write(2) will cause a SIGPIPE signal to be
   generated for the calling process."

So ECONNRESET is definitely not the right error to set on POLLERR,
though I'm still not sure what the right one would be (perhaps
EPIPE?).

Yes, if SIGPIPE is ignored, then that write() would produce EPIPE. So if
you're trying to emulate it via POLLERR, that would be accurate. Of
course it could fail for _other_ reasons, and I don't think we'd know
what those are without actually calling write(). Practically speaking,
though, if we know it's a pipe with a valid descriptor then any error is
basically equivalent to EPIPE (we don't care how, but for whatever
reason we couldn't write to the other end).

-Peff

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