log: --show-signature

This teaches the "log" family of commands to pass the GPG signature in the
commit objects to "gpg --verify" via the verify_signed_buffer() interface
used to verify signed tag objects. E.g.

    $ git show --show-signature -s HEAD

shows GPG output in the header part of the output.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/revision.c b/revision.c
index 8764dde..064e351 100644
--- a/revision.c
+++ b/revision.c
@@ -1469,6 +1469,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->show_notes = 1;
 		revs->show_notes_given = 1;
 		revs->notes_opt.use_default_notes = 1;
+	} else if (!strcmp(arg, "--show-signature")) {
+		revs->show_signature = 1;
 	} else if (!prefixcmp(arg, "--show-notes=") ||
 		   !prefixcmp(arg, "--notes=")) {
 		struct strbuf buf = STRBUF_INIT;