Merge branch 'jc/describe-misnamed-annotated-tag'

When "git describe C" finds an annotated tag with tagname A to be
the best name to explain commit C, and the tag is stored in a
"wrong" place in the refs/tags hierarchy, e.g. refs/tags/B, the
command gave a warning message but used A (not B) to describe C.
If C is exactly at the tag, the describe output would be "A", but
"git rev-parse A^0" would not be equal as "git rev-parse C^0".  The
behavior of the command has been changed to use the "long" form
i.e. A-0-gOBJECTNAME, which is correctly interpreted by rev-parse.

* jc/describe-misnamed-annotated-tag:
  describe: force long format for a name based on a mislocated tag

Author: gitster

builtin/describe.c

@@ -54,6 +54,7 @@ struct commit_name {
 	struct tag *tag;
 	unsigned prio:2; /* annotated tag = 2, tag = 1, head = 0 */
 	unsigned name_checked:1;
+	unsigned misnamed:1;
 	struct object_id oid;
 	char *path;
 };
@@ -132,6 +133,7 @@ static void add_to_known_names(const char *path,
 		e->tag = tag;
 		e->prio = prio;
 		e->name_checked = 0;
+		e->misnamed = 0;
 		oidcpy(&e->oid, oid);
 		free(e->path);
 		e->path = xstrdup(path);
@@ -275,10 +277,11 @@ static void append_name(struct commit_name *n, struct strbuf *dst)
 			die(_("annotated tag %s not available"), n->path);
 	}
 	if (n->tag && !n->name_checked) {
-		if (!n->tag->tag)
-			die(_("annotated tag %s has no embedded name"), n->path);
-		if (strcmp(n->tag->tag, all ? n->path + 5 : n->path))
-			warning(_("tag '%s' is really '%s' here"), n->tag->tag, n->path);
+		if (strcmp(n->tag->tag, all ? n->path + 5 : n->path)) {
+			warning(_("tag '%s' is externally known as '%s'"),
+				n->path, n->tag->tag);
+			n->misnamed = 1;
+		}
 		n->name_checked = 1;
 	}
 
@@ -314,7 +317,7 @@ static void describe_commit(struct object_id *oid, struct strbuf *dst)
 		 * Exact match to an existing ref.
 		 */
 		append_name(n, dst);
-		if (longformat)
+		if (n->misnamed || longformat)
 			append_suffix(0, n->tag ? get_tagged_oid(n->tag) : oid, dst);
 		if (suffix)
 			strbuf_addstr(dst, suffix);
@@ -463,7 +466,7 @@ static void describe_commit(struct object_id *oid, struct strbuf *dst)
 	}
 
 	append_name(all_matches[0].name, dst);
-	if (abbrev)
+	if (all_matches[0].name->misnamed || abbrev)
 		append_suffix(all_matches[0].depth, &cmit->object.oid, dst);
 	if (suffix)
 		strbuf_addstr(dst, suffix);

t/t6120-describe.sh

@@ -129,12 +129,30 @@ test_expect_success 'rename tag A to Q locally' '
 	mv .git/refs/tags/A .git/refs/tags/Q
 '
 cat - >err.expect <<EOF
-warning: tag 'A' is really 'Q' here
+warning: tag 'Q' is externally known as 'A'
 EOF
 check_describe A-* HEAD
 test_expect_success 'warning was displayed for Q' '
 	test_i18ncmp err.expect err.actual
 '
+test_expect_success 'misnamed annotated tag forces long output' '
+	description=$(git describe --no-long Q^0) &&
+	expr "$description" : "A-0-g[0-9a-f]*$" &&
+	git rev-parse --verify "$description" >actual &&
+	git rev-parse --verify Q^0 >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'abbrev=0 will not break misplaced tag (1)' '
+	description=$(git describe --abbrev=0 Q^0) &&
+	expr "$description" : "A-0-g[0-9a-f]*$"
+'
+
+test_expect_success 'abbrev=0 will not break misplaced tag (2)' '
+	description=$(git describe --abbrev=0 c^0) &&
+	expr "$description" : "A-1-g[0-9a-f]*$"
+'
+
 test_expect_success 'rename tag Q back to A' '
 	mv .git/refs/tags/Q .git/refs/tags/A
 '