[PATCH] Add the diff option --no-defaults

From: Johannes Schindelin <hidden>
Date: 2016-06-15 22:46:36
Subsystem: the rest · Maintainer: Linus Torvalds

It would be desirable to undo every setting in diff.defaultOptions
individually, but until there are options to reset every command
line option, there is the "--no-defaults" option (which can be
overridden by the "--defaults" option) to ignore the config setting.

Signed-off-by: Johannes Schindelin <redacted>
---

On Fri, 10 Apr 2009, Jeff King wrote:

On Thu, Apr 09, 2009 at 12:43:28PM +0200, Johannes Schindelin wrote:

quoted

Now, it is easy to put a patch on top of my patch to support something 
like --no-defaults.

No, it's not. We went over this in great detail earlier in the thread. 
If you want:

  git diff --no-defaults

then you basically have to parse twice to avoid the chicken-and-egg
problem.

So what?  We parse the config a gazillion times, and there we have to 
access the _disk_.

But the first parse is only looking for "--no-defaults". So you need to:

  1. Understand the semantics of the other options to correctly parse
     around them (i.e., knowing which ones take arguments).

  2. Parse the arguments without actually respecting most of them, since
     they will be parsed again later.

This would actually be pretty easy if we had a declarative structure
describing each option (like parseopt-ified options do). But the diff
options are parsed by a big conditional statement.

Two ways to make it easier would be:

  1. You could loosen (1) above by assuming that --no-defaults will
     never appears as the argument to an option, and therefore any time
     you find it, it should be respected. Thus your first parse is just
     a simple loop looking for the option.

  2. You could loosen (2) above by assuming that all options are
     idempotent. I don't know whether this is the case (I think it
     isn't for all git options, but a cursory look shows that it may be
     for diff options).

I go with 1)

 builtin-diff.c                  |    2 +-
 builtin-log.c                   |    8 ++++----
 diff.c                          |   29 ++++++++++++++++++++++-------
 diff.h                          |    2 +-
 t/t4037-diff-default-options.sh |    5 +++++
 5 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/builtin-diff.c b/builtin-diff.c
index d9a6e7d..8da0052 100644
--- a/builtin-diff.c
+++ b/builtin-diff.c

@@ -296,7 +296,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 
 	if (nongit)
 		die("Not a git repository");
-	parse_default_diff_options(&rev.diffopt);
+	argc = parse_default_diff_options(argc, argv, &rev.diffopt);
 	argc = setup_revisions(argc, argv, &rev, NULL);
 	if (!rev.diffopt.output_format) {
 		rev.diffopt.output_format = DIFF_FORMAT_PATCH;

diff --git a/builtin-log.c b/builtin-log.c
index e926774..2f36537 100644
--- a/builtin-log.c
+++ b/builtin-log.c

@@ -243,7 +243,7 @@ int cmd_whatchanged(int argc, const char **argv, const char *prefix)
 	init_revisions(&rev, prefix);
 	rev.diff = 1;
 	rev.simplify_history = 0;
-	parse_default_diff_options(&rev.diffopt);
+	argc = parse_default_diff_options(argc, argv, &rev.diffopt);
 	cmd_log_init(argc, argv, prefix, &rev);
 	if (!rev.diffopt.output_format)
 		rev.diffopt.output_format = DIFF_FORMAT_RAW;

@@ -315,7 +315,7 @@ int cmd_show(int argc, const char **argv, const char *prefix)
 	rev.always_show_header = 1;
 	rev.ignore_merges = 0;
 	rev.no_walk = 1;
-	parse_default_diff_options(&rev.diffopt);
+	argc = parse_default_diff_options(argc, argv, &rev.diffopt);
 	cmd_log_init(argc, argv, prefix, &rev);
 
 	count = rev.pending.nr;

@@ -383,7 +383,7 @@ int cmd_log_reflog(int argc, const char **argv, const char *prefix)
 	init_reflog_walk(&rev.reflog_info);
 	rev.abbrev_commit = 1;
 	rev.verbose_header = 1;
-	parse_default_diff_options(&rev.diffopt);
+	argc = parse_default_diff_options(argc, argv, &rev.diffopt);
 	cmd_log_init(argc, argv, prefix, &rev);
 
 	/*

@@ -415,7 +415,7 @@ int cmd_log(int argc, const char **argv, const char *prefix)
 
 	init_revisions(&rev, prefix);
 	rev.always_show_header = 1;
-	parse_default_diff_options(&rev.diffopt);
+	argc = parse_default_diff_options(argc, argv, &rev.diffopt);
 	cmd_log_init(argc, argv, prefix, &rev);
 	return cmd_log_walk(&rev);
 }

diff --git a/diff.c b/diff.c
index 6e76377..903dbb4 100644
--- a/diff.c
+++ b/diff.c

@@ -13,6 +13,7 @@
 #include "utf8.h"
 #include "userdiff.h"
 #include "sigchain.h"
+#include "parse-options.h"
 
 #ifdef NO_FAST_WORKING_DIRECTORY
 #define FAST_WORKING_DIRECTORY 0

@@ -2682,19 +2683,33 @@ static int default_diff_options(const char *key, const char *value, void *cb)
 	return 0;
 }
 
-void parse_default_diff_options(struct diff_options *options)
+int parse_default_diff_options(int real_argc, const char **real_argv,
+	struct diff_options *options)
 {
+	int use_defaults = 1;
+	struct option option[] = {
+		OPT_BOOLEAN(0, "defaults", &use_defaults, "use diff defaults"),
+		OPT_END()
+	};
 	char *default_options = NULL;
 	const char **argv;
 	int argc;
 
-	git_config(default_diff_options, &default_options);
-	if (!default_options)
-		return;
+	real_argc = parse_options(real_argc, real_argv, option, NULL,
+		PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_KEEP_UNKNOWN |
+		PARSE_OPT_NO_INTERNAL_HELP);
+
+	if (use_defaults) {
+		git_config(default_diff_options, &default_options);
+		if (!default_options)
+			return real_argc;
+
+		argc = split_cmdline(default_options, &argv);
+		diff_opt_parse(options, argv, argc);
+		free(argv);
+	}
 
-	argc = split_cmdline(default_options, &argv);
-	diff_opt_parse(options, argv, argc);
-	free(argv);
+	return real_argc;
 }
 
 static int parse_num(const char **cp_p)

diff --git a/diff.h b/diff.h
index e05e796..764e2f6 100644
--- a/diff.h
+++ b/diff.h

@@ -270,6 +270,6 @@ extern void diff_no_index(struct rev_info *, int, const char **, int, const char
 
 extern int index_differs_from(const char *def, int diff_flags);
 
-extern void parse_default_diff_options(struct diff_options *options);
+extern int parse_default_diff_options(int argc, const char **argv, struct diff_options *options);
 
 #endif /* DIFF_H */

diff --git a/t/t4037-diff-default-options.sh b/t/t4037-diff-default-options.sh
index 0284f7b..f57d65f 100755
--- a/t/t4037-diff-default-options.sh
+++ b/t/t4037-diff-default-options.sh

@@ -16,4 +16,9 @@ test_expect_success 'diff.defaultOptions' '
 	test 1 = $(wc -l < output)
 '
 
+test_expect_success '--no-defaults' '
+	git diff --no-defaults > output &&
+	! grep ^: output
+'
+
 test_done

-- 
1.6.2.1.613.g25746

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