ls-remote: add support for showing symrefs

Sometimes it's useful to know the main branch of a git repository
without actually downloading the repository.  This can be done by
looking at the symrefs stored in the remote repository.  Currently git
doesn't provide a simple way to show the symrefs stored on the remote
repository, even though the information is available.  Add a --symref
command line argument to the ls-remote command, which shows the symrefs
in the remote repository.

While there, replace a literal tab in the format string with \t to make
it more obvious to the reader.

Suggested-by: pedro rijo <pedrorijo91@gmail.com>
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-ls-remote.txt

@@ -10,7 +10,8 @@ SYNOPSIS
 --------
 [verse]
 'git ls-remote' [--heads] [--tags] [--refs] [--upload-pack=<exec>]
-	      [-q | --quiet] [--exit-code] [--get-url] [<repository> [<refs>...]]
+	      [-q | --quiet] [--exit-code] [--get-url]
+	      [--symref] [<repository> [<refs>...]]
 
 DESCRIPTION
 -----------
@@ -53,6 +54,12 @@ OPTIONS
 	"url.<base>.insteadOf" config setting (See linkgit:git-config[1]) and
 	exit without talking to the remote.
 
+--symref::
+	In addition to the object pointed by it, show the underlying
+	ref pointed by it when showing a symbolic ref.  Currently,
+	upload-pack only shows the symref HEAD, so it will be the only
+	one shown by ls-remote.
+
 <repository>::
 	The "remote" repository to query.  This parameter can be
 	either a URL or the name of a remote (see the GIT URLS and

builtin/ls-remote.c

@@ -5,7 +5,8 @@
 
 static const char * const ls_remote_usage[] = {
 	N_("git ls-remote [--heads] [--tags] [--refs] [--upload-pack=<exec>]\n"
-	   "                     [-q | --quiet] [--exit-code] [--get-url] [<repository> [<refs>...]]"),
+	   "                     [-q | --quiet] [--exit-code] [--get-url]\n"
+	   "                     [--symref] [<repository> [<refs>...]]"),
 	NULL
 };
 
@@ -37,6 +38,7 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 	int get_url = 0;
 	int quiet = 0;
 	int status = 0;
+	int show_symref_target = 0;
 	const char *uploadpack = NULL;
 	const char **pattern = NULL;
 
@@ -58,6 +60,8 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 			 N_("take url.<base>.insteadOf into account")),
 		OPT_SET_INT(0, "exit-code", &status,
 			    N_("exit with exit code 2 if no matching refs are found"), 2),
+		OPT_BOOL(0, "symref", &show_symref_target,
+			 N_("show underlying ref in addition to the object pointed by it")),
 		OPT_END()
 	};
 
@@ -101,7 +105,9 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 			continue;
 		if (!tail_match(pattern, ref->name))
 			continue;
-		printf("%s	%s\n", oid_to_hex(&ref->old_oid), ref->name);
+		if (show_symref_target && ref->symref)
+			printf("ref: %s\t%s\n", ref->symref, ref->name);
+		printf("%s\t%s\n", oid_to_hex(&ref->old_oid), ref->name);
 		status = 0; /* we found something */
 	}
 	return status;

t/t5512-ls-remote.sh

@@ -163,4 +163,49 @@ test_expect_success 'overrides work between mixed transfer/upload-pack hideRefs'
 	grep refs/tags/magic actual
 '
 
+test_expect_success 'ls-remote --symref' '
+	cat >expect <<-\EOF &&
+	ref: refs/heads/master	HEAD
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	HEAD
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/heads/master
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/remotes/origin/HEAD
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/remotes/origin/master
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/tags/mark
+	EOF
+	git ls-remote --symref >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'ls-remote with filtered symref (refname)' '
+	cat >expect <<-\EOF &&
+	ref: refs/heads/master	HEAD
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	HEAD
+	EOF
+	git ls-remote --symref . HEAD >actual &&
+	test_cmp expect actual
+'
+
+test_expect_failure 'ls-remote with filtered symref (--heads)' '
+	git symbolic-ref refs/heads/foo refs/tags/mark &&
+	cat >expect <<-\EOF &&
+	ref: refs/tags/mark	refs/heads/foo
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/heads/foo
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/heads/master
+	EOF
+	git ls-remote --symref --heads . >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'ls-remote --symref omits filtered-out matches' '
+	cat >expect <<-\EOF &&
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/heads/foo
+	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/heads/master
+	EOF
+	git ls-remote --symref --heads . >actual &&
+	test_cmp expect actual &&
+	git ls-remote --symref . "refs/heads/*" >actual &&
+	test_cmp expect actual
+'
+
+
 test_done