describe: prepend "tags/" when describing tags with embedded name

The man page of the "git describe" command explains the expected
output when using the --all option, i.e. the full reference path is
shown, including heads/ or tags/ prefix.

When 212945d4a8 ("Teach git-describe
to verify annotated tag names before output") made Git favor the
embedded name of annotated tags, it accidentally changed the output
format when the --all flag is given, only printing the tag's name
without the prefix.

Check if --all was specified and re-add the "tags/" prefix for this
special case to fix the regresssion.

Signed-off-by: Daniel Knittl-Frank <knittl89+git@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/describe.c

@@ -271,10 +271,13 @@ static void display_name(struct commit_name *n)
 		n->name_checked = 1;
 	}
 
-	if (n->tag)
+	if (n->tag) {
+		if (all)
+			printf("tags/");
 		printf("%s", n->tag->tag);
-	else
+	} else {
 		printf("%s", n->path);
+	}
 }
 
 static void show_suffix(int depth, const struct object_id *oid)

t/t6120-describe.sh

@@ -122,7 +122,7 @@ test_expect_success 'describe --contains defaults to HEAD without commit-ish' '
 '
 
 : >err.expect
-check_describe A --all A^0
+check_describe tags/A --all A^0
 test_expect_success 'no warning was displayed for A' '
 	test_cmp err.expect err.actual
 '
@@ -340,4 +340,8 @@ test_expect_success ULIMIT_STACK_SIZE 'describe works in a deep repo' '
 	test_cmp expect actual
 '
 
+check_describe tags/A --all A
+check_describe tags/c --all c
+check_describe heads/branch_A --all --match='branch_*' branch_A
+
 test_done