show-ref --verify: accept pseudorefs

"git show-ref --verify" is useful for scripts that want to look up a
fully qualified refname without falling back to the DWIM rules used by
"git rev-parse" rules when the ref does not exist. Currently it will
only accept "HEAD" or a refname beginning with "refs/". Running

    git show-ref --verify CHERRY_PICK_HEAD

will always result in

    fatal: 'CHERRY_PICK_HEAD' - not a valid ref

even when CHERRY_PICK_HEAD exists. By calling refname_is_safe() instead
of comparing the refname to "HEAD" we can accept all one-level refs that
contain only uppercase ascii letters and underscores.

Signed-off-by: Phillip Wood <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: phillipwood

builtin/show-ref.c

@@ -172,7 +172,7 @@ static int cmd_show_ref__verify(const struct show_one_options *show_one_opts,
 	while (*refs) {
 		struct object_id oid;
 
-		if ((starts_with(*refs, "refs/") || !strcmp(*refs, "HEAD")) &&
+		if ((starts_with(*refs, "refs/") || refname_is_safe(*refs)) &&
 		    !read_ref(*refs, &oid)) {
 			show_one(show_one_opts, *refs, &oid);
 		}

t/t1403-show-ref.sh

@@ -174,6 +174,14 @@ test_expect_success 'show-ref --verify HEAD' '
 	test_must_be_empty actual
 '
 
+test_expect_success 'show-ref --verify pseudorefs' '
+	git update-ref CHERRY_PICK_HEAD HEAD $ZERO_OID &&
+	test_when_finished "git update-ref -d CHERRY_PICK_HEAD" &&
+	git show-ref -s --verify HEAD >actual &&
+	git show-ref -s --verify CHERRY_PICK_HEAD >expect &&
+	test_cmp actual expect
+'
+
 test_expect_success 'show-ref --verify with dangling ref' '
 	sha1_file() {
 		echo "$*" | sed "s#..#.git/objects/&/#"