diff: teach diff.relative to give default to --relative=<value>bp/diff-relative-config

Setting diff.relative configuration variable to true makes 'git diff'
behave as if '--relative=true' was passed on the command line.

Signed-off-by: Brandon Phillips <kelson@shysecurity.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 34 insertions, 0 deletions

diff --git a/Documentation/diff-config.txt b/Documentation/diff-config.txt
index b001779520..b8a7c600c8 100644
--- a/Documentation/diff-config.txt
+++ b/Documentation/diff-config.txt
@@ -103,6 +103,12 @@ diff.orderfile::
 	one shell glob pattern per line.
 	Can be overridden by the '-O' option to linkgit:git-diff[1].
 
+diff.relative::
+	Show pathnames relative to the current directory and exclude
+	changes outside this directory; equivalent to the 'git diff'
+	option '--relative'.
+	Overridden by the '--no-relative' linkgit:git-diff[1] option.
+
 diff.renameLimit::
 	The number of files to consider when performing the copy/rename
 	detection; equivalent to the 'git diff' option '-l'.
diff --git a/diff.c b/diff.c
index 7bceba88d2..9e4ec1f8a7 100644
--- a/diff.c
+++ b/diff.c
@@ -223,6 +223,14 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
+	if (!strcmp(var, "diff.relative")) {
+		if (git_config_bool(var, value))
+			DIFF_OPT_SET(&default_diff_options, RELATIVE_NAME);
+		else
+			DIFF_OPT_CLR(&default_diff_options, RELATIVE_NAME);
+		return 0;
+	}
+
 	if (git_color_config(var, value, cb) < 0)
 		return -1;
 
diff --git a/t/t4045-diff-relative.sh b/t/t4045-diff-relative.sh
index ccd67c77ba..c2c15e4cf5 100755
--- a/t/t4045-diff-relative.sh
+++ b/t/t4045-diff-relative.sh
@@ -104,10 +104,30 @@ test_expect_success "--raw $*" "
 "
 }
 
+check_config() {
+store_diff_relative $1; shift
+test_expect_success "git-config diff.relative=true in $1" "
+	(cd $1; git -c diff.relative=true diff -p HEAD^ >../actual) &&
+	test_cmp expected actual
+"
+}
+
+check_config_no_relative() {
+store_diff_absolute $1; shift
+test_expect_success "--no-relative w/ git-config diff.relative=true in $1" "
+	(cd $1; git -c diff.relative=true diff --no-relative -p HEAD^ >../actual) &&
+	test_cmp expected actual
+"
+}
+
 for type in diff numstat stat raw norel_pre norel_post; do
 	check_$type file2 --relative=subdir/
 	check_$type file2 --relative=subdir
 	check_$type dir/file2 --relative=sub
 done
+for type in config config_no_relative; do
+	check_$type file2 subdir/
+	check_$type file2 subdir
+done
 
 test_done