branch: support configuring --sort via .gitconfig

Add support for configuring default sort ordering for git branches. Command
line option will override this configured value, using the exact same
syntax.

Signed-off-by: Samuel Maftoul <samuel.maftoul@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -1039,6 +1039,12 @@ branch.autoSetupRebase::
 	branch to track another branch.
 	This option defaults to never.
 
+branch.sort::
+	This variable controls the sort ordering of branches when displayed by
+	linkgit:git-branch[1]. Without the "--sort=<value>" option provided, the
+	value of this variable will be used as the default.
+	See linkgit:git-for-each-ref[1] field names for valid values.
+
 branch.<name>.remote::
 	When on branch <name>, it tells 'git fetch' and 'git push'
 	which remote to fetch from/push to.  The remote to push to

Documentation/git-branch.txt

@@ -268,10 +268,11 @@ start-point is either a local or remote-tracking branch.
 	order of the value. You may use the --sort=<key> option
 	multiple times, in which case the last key becomes the primary
 	key. The keys supported are the same as those in `git
-	for-each-ref`. Sort order defaults to sorting based on the
+	for-each-ref`. Sort order defaults to the value configured for the
+	`branch.sort` variable if exists, or to sorting based on the
 	full refname (including `refs/...` prefix). This lists
 	detached HEAD (if present) first, then local branches and
-	finally remote-tracking branches.
+	finally remote-tracking branches. See linkgit:git-config[1].
 
 
 --points-at <object>::

builtin/branch.c

@@ -74,6 +74,14 @@ define_list_config_array(color_branch_slots);
 static int git_branch_config(const char *var, const char *value, void *cb)
 {
 	const char *slot_name;
+	struct ref_sorting **sorting_tail = (struct ref_sorting **)cb;
+
+	if (!strcmp(var, "branch.sort")) {
+		if (!value)
+			return config_error_nonbool(var);
+		parse_ref_sorting(sorting_tail, value);
+		return 0;
+	}
 
 	if (starts_with(var, "column."))
 		return git_column_config(var, value, "branch", &colopts);
@@ -653,7 +661,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage_with_options(builtin_branch_usage, options);
 
-	git_config(git_branch_config, NULL);
+	git_config(git_branch_config, sorting_tail);
 
 	track = git_branch_track;
 

t/t3200-branch.sh

@@ -1305,4 +1305,50 @@ test_expect_success 'tracking with unexpected .fetch refspec' '
 	)
 '
 
+test_expect_success 'configured committerdate sort' '
+	git init sort &&
+	(
+		cd sort &&
+		git config branch.sort committerdate &&
+		test_commit initial &&
+		git checkout -b a &&
+		test_commit a &&
+		git checkout -b c &&
+		test_commit c &&
+		git checkout -b b &&
+		test_commit b &&
+		git branch >actual &&
+		cat >expect <<-\EOF &&
+		  master
+		  a
+		  c
+		* b
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'option override configured sort' '
+	(
+		cd sort &&
+		git config branch.sort committerdate &&
+		git branch --sort=refname >actual &&
+		cat >expect <<-\EOF &&
+		  a
+		* b
+		  c
+		  master
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'invalid sort parameter in configuration' '
+	(
+		cd sort &&
+		git config branch.sort "v:notvalid" &&
+		test_must_fail git branch
+	)
+'
+
 test_done