[PATCH v7 4/6] object-name: show date for ambiguous tag objects

Make the ambiguous tag object output nicer in the case of tag objects
such as ebf3c04b262 (Git 2.32, 2021-06-06) by including the date in
the "tagger" header. I.e.:

    $ git rev-parse b7e68
    error: short object ID b7e68 is ambiguous
    hint: The candidates are:
    hint:   b7e68c41d92 tag 2021-06-06 - v2.32.0
    hint:   b7e68ae18e0 commit 2019-12-23 - bisect: use the standard 'if (!var)' way to check for 0
    hint:   b7e68f6b413 tree
    hint:   b7e68490b97 blob
    b7e68
    [...]

Before this we'd emit a "tag" line of:

    hint:   b7e68c41d92 tag v2.32.0

As with OBJ_COMMIT we punt on the cases where the date in the object
is nonsensical, and other cases where parse_tag() might fail. For
those we'll use our default date of "0" and tag message of
"". E.g. for some of the corrupt tags created by t3800-mktag.sh we'd
emit a line like:

    hint:   8d62cb0b06 tag 1970-01-01 -

We could detect that and emit a "%s [bad tag object]" message (to go
with the existing generic "%s [bad object]"), but I don't think it's
worth the effort. Users are unlikely to ever run into cases where
they've got a broken object that's also ambiguous, and in case they do
output that's a bit nonsensical beats wasting translator time on this
obscure edge case.

We should instead change parse_tag_buffer() to be more eager to emit
an error() instead of silently aborting with "return -1;". In the case
of "t3800-mktag.sh" it takes the "size < the_hash_algo->hexsz + 24"
branch.

Signed-off-by: Ævar Arnfjörð Bjarmason <redacted>
---
 object-name.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/object-name.c b/object-name.c
index 743f346842a..7c6cb60ceff 100644
--- a/object-name.c
+++ b/object-name.c

@@ -403,20 +403,25 @@ static int show_ambiguous_object(const struct object_id *oid, void *data)
 	} else if (type == OBJ_TAG) {
 		struct tag *tag = lookup_tag(ds->repo, oid);
 		const char *tag_tag = "";
+		timestamp_t tag_date = 0;
 
-		if (!parse_tag(tag) && tag->tag)
+		if (!parse_tag(tag) && tag->tag) {
 			tag_tag = tag->tag;
+			tag_date = tag->date;
+		}
 
 		/*
 		 * TRANSLATORS: This is a line of
 		 * ambiguous tag object output. E.g.:
 		 *
-		 *    "deadbeef tag Some Tag Message"
+		 *    "deadbeef tag 2021-01-01 - Some Tag Message"
 		 *
 		 * The second argument is the "tag" string from
 		 * object.c.
 		 */
-		strbuf_addf(&desc, _("%s tag %s"), hash, tag_tag);
+		strbuf_addf(&desc, _("%s tag %s - %s"), hash,
+			    show_date(tag_date, 0, DATE_MODE(SHORT)),
+			    tag_tag);
 	} else if (type == OBJ_TREE) {
 		/*
 		 * TRANSLATORS: This is a line of ambiguous <type>

-- 
2.34.1.1373.g062f5534af2