Re: [PATCH] Add diff.context option to specify default context

Jeff Muizelaar [off-list ref] writes:

This adds a diff.context config option to allow specifying
the number of lines of context. This is similar to Mercurial's
'unified' option.

Random thoughts.

* Please refer to Documentation/SubmittingPatches.  Saving your
  message in a mbox and applying it would produce this crap:

    commit ba4c972eacb91058f1317dbcd4ff77b471fa938e
    Author: Jeff Muizelaar [off-list ref]
    Date:   Fri Sep 14 14:16:03 2012 -0400

        Add diff.context option to specify default context

        This adds a diff.context config option to allow specifying
        the number of lines of context. This is similar to Mercurial's
        'unified' option.

        commit 1bd81c75de6824c39852bc8516acd0733737ed83
        Author: Jeff Muizelaar [off-list ref]
        Date:   Fri Sep 14 13:55:02 2012 -0400

            [PATCH] Add diff.context option to specify default context

            This adds a diff.context config option to allow specifying
            the number of lines of context. This is similar to
            Mercurial's
            'unified' option.

  which is not acceptable.

* Sign-off your patch.

* Citing similaritly to options in other systems does not add much
  value for people who read the proposed log message.  In this case,
  I think the first sentence is written clearly enough that it is
  sufficient without such clarification.  If anything, it should
  instead say:

	diff: diff.context configuration gives default to -U

	Introduce a configuration variable diff.context that tells
	Porcelain commands to use a non-default number of context
	lines instead of 3 (the default).  With this variable, users
	do not have to keep repeating "git log -U8" from the command
	line; instead, it becomes sufficient to say "git config
	diff.context 8" just once.

  or something like that to make it clear that it is related to our
  -U option.

* That relationship with the -U option may worth mentioning in the
  documentation, not just in the log message.

* The configuration is read only in diff_ui_config and not in the
  lower-level diff_config.  What the patch does is the right thing.

  It however needs to be documented in the patch to diff-config.txt
  that it affects only the Porcelain commands, and does not break
  plumbing commands.

* Tests?  Minimally, the cases you may want to check are:

  - What happens with various values set to this variable, and does
    the code properly diagnose errors?

    [diff]
	context ;# boolean?
        context = no
        context = 0
        context = -1
        context = 8

  - What happens when the variable is set and the command line gives
    a different value with -U?

    git config diff.context 8
    git log -U4 -1

  - Does it really keep plumbing intact?

    git config diff.context 8
    git diff-files -p


Thanks.

Introduce a configuration variable diff.context that tells
Porcelain commands to use a non-default number of context
lines instead of 3 (the default).  With this variable, users
do not have to keep repeating "git log -U8" from the command
line; instead, it becomes sufficient to say "git config
diff.context 8" just once.

Signed-off-by: Jeff Muizelaar <redacted>
---
 Documentation/diff-config.txt |    4 +
 diff.c                        |    9 +++-
 t/t4060-diff-context.sh       |  127 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 139 insertions(+), 1 deletions(-)
 create mode 100755 t/t4060-diff-context.sh

diff --git a/Documentation/diff-config.txt b/Documentation/diff-config.txt
index 67a90a8..75ab8a5 100644
--- a/Documentation/diff-config.txt
+++ b/Documentation/diff-config.txt

@@ -56,6 +56,10 @@ diff.statGraphWidth::
 	Limit the width of the graph part in --stat output. If set, applies
 	to all commands generating --stat output except format-patch.
 
+diff.context::
+	Generate diffs with <n> lines of context instead of the default of
+	3. This value is overridden by the -U option.
+
 diff.external::
 	If this config variable is set, diff generation is not
 	performed using the internal diff machinery, but using the

diff --git a/diff.c b/diff.c
index 35d3f07..86e5f2a 100644
--- a/diff.c
+++ b/diff.c

@@ -26,6 +26,7 @@ static int diff_detect_rename_default;
 static int diff_rename_limit_default = 400;
 static int diff_suppress_blank_empty;
 static int diff_use_color_default = -1;
+static int diff_context_default = 3;
 static const char *diff_word_regex_cfg;
 static const char *external_diff_cmd_cfg;
 int diff_auto_refresh_index = 1;

@@ -141,6 +142,12 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 		diff_use_color_default = git_config_colorbool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "diff.context")) {
+		diff_context_default = git_config_int(var, value);
+		if (diff_context_default < 0)
+			return -1;
+		return 0;
+	}
 	if (!strcmp(var, "diff.renames")) {
 		diff_detect_rename_default = git_config_rename(var, value);
 		return 0;

@@ -3170,7 +3177,7 @@ void diff_setup(struct diff_options *options)
 	options->break_opt = -1;
 	options->rename_limit = -1;
 	options->dirstat_permille = diff_dirstat_permille_default;
-	options->context = 3;
+	options->context = diff_context_default;
 	DIFF_OPT_SET(options, RENAME_EMPTY);
 
 	options->change = diff_change;

diff --git a/t/t4060-diff-context.sh b/t/t4060-diff-context.sh
new file mode 100755
index 0000000..76fa3c3
--- /dev/null
+++ b/t/t4060-diff-context.sh

@@ -0,0 +1,127 @@
+#!/bin/sh
+#
+# Copyright (c) 2012 Mozilla Foundation
+#
+
+test_description='diff.context configuration'
+
+. ./test-lib.sh
+
+cat << EOF > x
+firstline
+b
+c
+d
+e
+f
+preline
+postline
+i
+j
+k
+l
+m
+n
+EOF
+test_expect_success 'initial add' '
+	git update-index --add x &&
+	git commit -m initial
+'
+
+cat << EOF > x
+firstline
+b
+c
+d
+e
+f
+preline
+1
+postline
+i
+j
+k
+l
+m
+n
+EOF
+
+test_expect_success 'next commit' '
+	git update-index --add x &&
+	git commit -m next
+'
+cat << EOF > x
+firstline
+b
+c
+d
+e
+f
+preline
+2
+postline
+i
+j
+k
+l
+m
+n
+EOF
+
+
+
+
+test_expect_success 'diff.context affects log' '
+	git log -1 -p | grep -q -v firstline
+	git config diff.context 8 &&
+	git log -1 -p | grep -q firstline
+'
+test_expect_success 'different -U value' '
+	git config diff.context 8 &&
+	git log -U4 -1 | grep -q -v firstline
+'
+
+test_expect_success 'diff.context affects diff' '
+	git config diff.context 8 &&
+	git diff | grep -q firstline
+'
+
+test_expect_success 'plumbing not affected' '
+	git config diff.context 8 &&
+	git diff-files -p | grep -q -v firstline
+'
+
+cat > .git/config << EOF
+[diff]
+	context = no
+EOF
+test_expect_success 'config parsing' '
+	git diff 2>&1 | grep -q "bad config value"
+'
+
+cat > .git/config << EOF
+[diff]
+	context = 0
+EOF
+test_expect_success 'config parsing' '
+	git diff | grep -v preline
+'
+
+cat > .git/config << EOF
+[diff]
+	context = -1
+EOF
+test_expect_success 'config parsing' '
+	git diff 2>&1 | grep -q "bad config file"
+'
+
+cat > .git/config << EOF
+[diff]
+	context = 8
+EOF
+test_expect_success 'config parsing' '
+	git diff 2>&1 | grep "postline"
+'
+
+
+test_done

-- 
1.7.4.4