branch: add '--points-at' option

Add the '--points-at' option provided by 'ref-filter'. The option lets
the user to list only branches which points at the given object.

Add documentation and tests for the same.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-branch.txt

@@ -11,7 +11,8 @@ SYNOPSIS
 'git branch' [--color[=<when>] | --no-color] [-r | -a]
 	[--list] [-v [--abbrev=<length> | --no-abbrev]]
 	[--column[=<options>] | --no-column]
-	[(--merged | --no-merged | --contains) [<commit>]] [--sort=<key>] [<pattern>...]
+	[(--merged | --no-merged | --contains) [<commit>]] [--sort=<key>]
+	[--points-at <object>] [<pattern>...]
 'git branch' [--set-upstream | --track | --no-track] [-l] [-f] <branchname> [<start-point>]
 'git branch' (--set-upstream-to=<upstream> | -u <upstream>) [<branchname>]
 'git branch' --unset-upstream [<branchname>]
@@ -240,6 +241,9 @@ start-point is either a local or remote-tracking branch.
 	finally remote-tracking branches.
 
 
+--points-at <object>::
+	Only list branches of the given object.
+
 Examples
 --------
 

builtin/branch.c

@@ -26,6 +26,7 @@ static const char * const builtin_branch_usage[] = {
 	N_("git branch [<options>] [-l] [-f] <branch-name> [<start-point>]"),
 	N_("git branch [<options>] [-r] (-d | -D) <branch-name>..."),
 	N_("git branch [<options>] (-m | -M) [<old-branch>] <new-branch>"),
+	N_("git branch [<options>] [-r | -a] [--points-at]"),
 	NULL
 };
 
@@ -646,6 +647,10 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		OPT_COLUMN(0, "column", &colopts, N_("list branches in columns")),
 		OPT_CALLBACK(0 , "sort", sorting_tail, N_("key"),
 			     N_("field name to sort on"), &parse_opt_ref_sorting),
+		{
+			OPTION_CALLBACK, 0, "points-at", &filter.points_at, N_("object"),
+			N_("print only branches of the object"), 0, parse_opt_object_name
+		},
 		OPT_END(),
 	};
 
@@ -674,7 +679,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	if (!delete && !rename && !edit_description && !new_upstream && !unset_upstream && argc == 0)
 		list = 1;
 
-	if (filter.with_commit || filter.merge != REF_FILTER_MERGED_NONE)
+	if (filter.with_commit || filter.merge != REF_FILTER_MERGED_NONE || filter.points_at.nr)
 		list = 1;
 
 	if (!!delete + !!rename + !!new_upstream +

t/t3203-branch-output.sh

@@ -154,4 +154,13 @@ test_expect_success 'git branch `--sort` option' '
 	test_i18ncmp expect actual
 '
 
+test_expect_success 'git branch --points-at option' '
+	cat >expect <<-\EOF &&
+	  branch-one
+	  master
+	EOF
+	git branch --points-at=branch-one >actual &&
+	test_cmp expect actual
+'
+
 test_done