[PATCH v3 3/5] pretty: add support for "valueonly" option in %(trailers)

[Anders Waldenborg <anders@0x63.nu>]

With the new "key=" option to %(trailers) it often makes little sense to
show the key, as it by definition already is know 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>
---
 Documentation/pretty-formats.txt | 2 ++
 pretty.c                         | 2 ++
 t/t4205-log-pretty-formats.sh    | 6 ++++++
 trailer.c                        | 6 ++++--
 trailer.h                        | 1 +
 5 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 75c2e838d..8cc8c3f9f 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -216,6 +216,8 @@ endif::git-rev-list[]
   ** 'key=<K>': only show trailers with specified key. Matching is
      done case-insensitively and trailing colon is optional. If option
      is given multiple times only last one is used.
+  ** 'valueonly': skip over the key part of the trailer and only show
+     the its value part.
   ** Examples: `%(trailers:only,unfold)` unfolds and shows all trailer
      lines, `%(trailers:key=Reviewed-by,unfold)` unfolds and shows
      trailer lines with key `Reviewed-by`.
diff --git a/pretty.c b/pretty.c
index aaedc8447..2e99f2418 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1335,6 +1335,8 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 					opts.only_trailers = 1;
 				else if (match_placeholder_arg(arg, "unfold", &arg))
 					opts.unfold = 1;
+				else if (match_placeholder_arg(arg, "valueonly", &arg))
+					opts.value_only = 1;
 				else if (skip_prefix(arg, "key=", &arg)) {
 					const char *end = arg + strcspn(arg, ",)");
 
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index aba7ba206..095208d6b 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -634,6 +634,12 @@ test_expect_success '%(trailers:key=foo,unfold) properly unfolds' '
 	test_cmp expect actual
 '
 
+test_expect_success '%(trailers:key=foo,valueonly) shows only value' '
+	git log --no-walk --pretty="format:%(trailers:key=Acked-by,valueonly)" >actual &&
+	echo "A U Thor <author@example.com>" >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'trailer parsing not fooled by --- line' '
 	git commit --allow-empty -F - <<-\EOF &&
 	this is the subject
diff --git a/trailer.c b/trailer.c
index 97c8f2762..662c7ff03 100644
--- a/trailer.c
+++ b/trailer.c
@@ -1150,8 +1150,10 @@ static void format_trailer_info(struct strbuf *out,
 			if (!opts->filter || opts->filter(&tok, opts->filter_data)) {
 				if (opts->unfold)
 					unfold_value(&val);
-
-				strbuf_addf(out, "%s: %s\n", tok.buf, val.buf);
+				if (!opts->value_only)
+					strbuf_addf(out, "%s: ", tok.buf);
+				strbuf_addbuf(out, &val);
+				strbuf_addch(out, '\n');
 			}
 			strbuf_release(&tok);
 			strbuf_release(&val);
diff --git a/trailer.h b/trailer.h
index 5255b676d..06d417fe9 100644
--- a/trailer.h
+++ b/trailer.h
@@ -72,6 +72,7 @@ struct process_trailer_options {
 	int only_input;
 	int unfold;
 	int no_divider;
+	int value_only;
 	int (*filter)(const struct strbuf *, void *);
 	void *filter_data;
 };
-- 
2.17.1