[RFC/PATCH] git symbolic-ref --delete $symref

[Johan Herland <johan@herland.net>]

Teach symbolic-ref to delete symrefs by adding the -d/--delete option to
git-symbolic-ref. Both proper and dangling symrefs are deleted by this
option, but other refs - or anything else that is not a symref - is not.

The symref deletion is performed by first verifying that we are given a
proper symref, and then invoking delete_ref() on it with the REF_NODEREF
flag.

Signed-off-by: Johan Herland <johan@herland.net>
---

Here is a quick first attempt at implementing the 'git symbolic-ref -d'
you've been mentioning in the symref deletion thread.

 Documentation/git-symbolic-ref.txt | 10 +++++++++-
 builtin/symbolic-ref.c             | 33 +++++++++++++++++++++++----------
 t/t1401-symbolic-ref.sh            | 30 ++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+), 11 deletions(-)

diff --git a/Documentation/git-symbolic-ref.txt b/Documentation/git-symbolic-ref.txt
index 981d3a8..ef68ad2 100644
--- a/Documentation/git-symbolic-ref.txt
+++ b/Documentation/git-symbolic-ref.txt
@@ -3,13 +3,14 @@ git-symbolic-ref(1)

 NAME
 ----
-git-symbolic-ref - Read and modify symbolic refs
+git-symbolic-ref - Read, modify and delete symbolic refs

 SYNOPSIS
 --------
 [verse]
 'git symbolic-ref' [-m <reason>] <name> <ref>
 'git symbolic-ref' [-q] [--short] <name>
+'git symbolic-ref' --delete [-q] <name>

 DESCRIPTION
 -----------
@@ -21,6 +22,9 @@ argument to see which branch your working tree is on.
 Given two arguments, creates or updates a symbolic ref <name> to
 point at the given branch <ref>.

+Given `--delete` and an additional argument, deletes the given
+symbolic ref.
+
 A symbolic ref is a regular file that stores a string that
 begins with `ref: refs/`.  For example, your `.git/HEAD` is
 a regular file whose contents is `ref: refs/heads/master`.
@@ -28,6 +32,10 @@ a regular file whose contents is `ref: refs/heads/master`.
 OPTIONS
 -------

+-d::
+--delete::
+	Delete the symbolic ref <name>.
+
 -q::
 --quiet::
 	Do not issue an error message if the <name> is not a
diff --git a/builtin/symbolic-ref.c b/builtin/symbolic-ref.c
index 9e92828..f481959 100644
--- a/builtin/symbolic-ref.c
+++ b/builtin/symbolic-ref.c
@@ -5,12 +5,11 @@

 static const char * const git_symbolic_ref_usage[] = {
 	N_("git symbolic-ref [options] name [ref]"),
+	N_("git symbolic-ref -d [-q] name"),
 	NULL
 };

-static int shorten;
-
-static void check_symref(const char *HEAD, int quiet)
+static int check_symref(const char *HEAD, int quiet, int shorten, int print)
 {
 	unsigned char sha1[20];
 	int flag;
@@ -22,20 +21,24 @@ static void check_symref(const char *HEAD, int quiet)
 		if (!quiet)
 			die("ref %s is not a symbolic ref", HEAD);
 		else
-			exit(1);
+			return 1;
+	}
+	if (print) {
+		if (shorten)
+			refname = shorten_unambiguous_ref(refname, 0);
+		puts(refname);
 	}
-	if (shorten)
-		refname = shorten_unambiguous_ref(refname, 0);
-	puts(refname);
+	return 0;
 }

 int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 {
-	int quiet = 0;
+	int quiet = 0, delete = 0, shorten = 0, ret = 0;
 	const char *msg = NULL;
 	struct option options[] = {
 		OPT__QUIET(&quiet,
 			N_("suppress error message for non-symbolic (detached) refs")),
+		OPT_BOOL('d', "delete", &delete, N_("delete symbolic ref")),
 		OPT_BOOL(0, "short", &shorten, N_("shorten ref output")),
 		OPT_STRING('m', NULL, &msg, N_("reason"), N_("reason of the update")),
 		OPT_END(),
@@ -46,9 +49,19 @@ int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 			     git_symbolic_ref_usage, 0);
 	if (msg &&!*msg)
 		die("Refusing to perform update with empty message");
+
+	if (delete) {
+		if (argc != 1)
+			usage_with_options(git_symbolic_ref_usage, options);
+		ret = check_symref(argv[0], 1, 0, 0);
+		if (ret)
+			die("Cannot delete %s, not a symbolic ref", argv[0]);
+		return delete_ref(argv[0], NULL, REF_NODEREF);
+	}
+
 	switch (argc) {
 	case 1:
-		check_symref(argv[0], quiet);
+		ret = check_symref(argv[0], quiet, shorten, 1);
 		break;
 	case 2:
 		if (!strcmp(argv[0], "HEAD") &&
@@ -59,5 +72,5 @@ int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 	default:
 		usage_with_options(git_symbolic_ref_usage, options);
 	}
-	return 0;
+	return ret;
 }
diff --git a/t/t1401-symbolic-ref.sh b/t/t1401-symbolic-ref.sh
index 2c96551..36378b0 100755
--- a/t/t1401-symbolic-ref.sh
+++ b/t/t1401-symbolic-ref.sh
@@ -33,4 +33,34 @@ test_expect_success 'symbolic-ref refuses bare sha1' '
 '
 reset_to_sane

+test_expect_success 'symbolic-ref deletes HEAD' '
+	git symbolic-ref -d HEAD &&
+	test_path_is_file .git/refs/heads/foo &&
+	test_path_is_missing .git/HEAD
+'
+reset_to_sane
+
+test_expect_success 'symbolic-ref deletes dangling HEAD' '
+	git symbolic-ref HEAD refs/heads/missing &&
+	git symbolic-ref -d HEAD &&
+	test_path_is_missing .git/refs/heads/missing &&
+	test_path_is_missing .git/HEAD
+'
+reset_to_sane
+
+test_expect_success 'symbolic-ref fails to delete missing FOO' '
+	echo "fatal: Cannot delete FOO, not a symbolic ref" >expect &&
+	test_must_fail git symbolic-ref -d FOO >actual 2>&1 &&
+	test_cmp expect actual
+'
+reset_to_sane
+
+test_expect_success 'symbolic-ref fails to delete real ref' '
+	echo "fatal: Cannot delete refs/heads/foo, not a symbolic ref" >expect &&
+	test_must_fail git symbolic-ref -d refs/heads/foo >actual 2>&1 &&
+	test_path_is_file .git/refs/heads/foo &&
+	test_cmp expect actual
+'
+reset_to_sane
+
 test_done
--
1.7.12.1.609.g5cd6968