pretty: add support for "valueonly" option in %(trailers)

With the new "key=" option to %(trailers) it often makes little sense to
show the key, as it by definition already is knows which trailer is
printed there. This new "valueonly" option makes it omit the key when
printing trailers.

E.g.:
 $ git show -s --pretty='%s%n%(trailers:key=Signed-off-by,valueonly)' aaaa88182
will show:
 > upload-pack: fix broken if/else chain in config callback
 > Jeff King <peff@peff.net>
 > Junio C Hamano <gitster@pobox.com>

Signed-off-by: Anders Waldenborg <anders@0x63.nu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/pretty.c b/pretty.c
index 5bf05cde56..fe73916adc 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1391,7 +1391,8 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 					opts.filter_data = &filter_list;
 					opts.only_trailers = 1;
 				} else if (!match_placeholder_bool_arg(arg, "only", &arg, &opts.only_trailers) &&
-					   !match_placeholder_bool_arg(arg, "unfold", &arg, &opts.unfold))
+					   !match_placeholder_bool_arg(arg, "unfold", &arg, &opts.unfold) &&
+					   !match_placeholder_bool_arg(arg, "valueonly", &arg, &opts.value_only))
 					break;
 			}
 		}