object-name: show date for ambiguous tag objects

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 without a date, e.g.:

    hint:   b7e68c41d92 tag v2.32.0

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>