pretty: add %(describe)

Add a format placeholder for describe output.  Implement it by actually
calling git describe, which is simple and guarantees correctness.  It's
intended to be used with $Format:...$ in files with the attribute
export-subst and git archive.  It can also be used with git log etc.,
even though that's going to be slow due to the fork for each commit.

Suggested-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

0 files changed, 0 insertions, 0 deletions