[PATCH 5/5] pretty format %(trailers): add a "key_value_separator"

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

As noted in a previous commit which added "keyonly" it's needlessly
hard to use the "log" machinery to produce machine-readable output for
%(trailers). with the combination of the existing "separator" and this
new "key_value_separator" this becomes trivial, as seen by the test
being added here.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Documentation/pretty-formats.txt |  4 ++++
 pretty.c                         |  9 +++++++++
 t/t4205-log-pretty-formats.sh    | 22 ++++++++++++++++++++++
 trailer.c                        |  8 ++++++--
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index d080f0d2476..369d243eae9 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -286,6 +286,10 @@ multiple times the last occurance wins.
    `%(trailers:only,unfold=true)` unfolds and shows all trailer lines.
 ** 'keyonly[=bool]': only show the key part of the trailer.
 ** 'valueonly[=bool]': only show the value part of the trailer.
+** 'key_value_separator=<SEP>': specify a separator inserted between
+   trailer lines. When this option is not given each trailer key-value
+   pair separated by ": ". Otherwise it shares the same semantics as 
+   'separator=<SEP>' above.
 
 NOTE: Some placeholders may depend on other options given to the
 revision traversal engine. For example, the `%g*` reflog options will
diff --git a/pretty.c b/pretty.c
index d989a6ae712..dea77f2621a 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1421,6 +1421,7 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 		struct process_trailer_options opts = PROCESS_TRAILER_OPTIONS_INIT;
 		struct string_list filter_list = STRING_LIST_INIT_NODUP;
 		struct strbuf sepbuf = STRBUF_INIT;
+		struct strbuf kvsepbuf = STRBUF_INIT;
 		size_t ret = 0;
 
 		opts.no_divider = 1;
@@ -1454,6 +1455,14 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 					strbuf_expand(&sepbuf, fmt, strbuf_expand_literal_cb, NULL);
 					free(fmt);
 					opts.separator = &sepbuf;
+				} else if (match_placeholder_arg_value(arg, "key_value_separator", &arg, &argval, &arglen)) {
+					char *fmt;
+
+					strbuf_reset(&kvsepbuf);
+					fmt = xstrndup(argval, arglen);
+					strbuf_expand(&kvsepbuf, fmt, strbuf_expand_literal_cb, NULL);
+					free(fmt);
+					opts.key_value_separator = &kvsepbuf;
 				} 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, "keyonly", &arg, &opts.key_only) &&
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index e1100082b34..47b3f7d67c4 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -765,6 +765,28 @@ test_expect_success 'pretty format %(trailers:separator) changes separator' '
 	test_cmp expect actual
 '
 
+test_expect_success 'pretty format %(trailers:key_value_separator) changes key-value separator' '
+	git log --no-walk --pretty=format:"X%(trailers:key_value_separator=%x00,unfold)X" >actual &&
+	(
+		printf "XSigned-off-by\0A U Thor <author@example.com>\n" &&
+		printf "Acked-by\0A U Thor <author@example.com>\n" &&
+		printf "[ v2 updated patch description ]\n" &&
+		printf "Signed-off-by\0A U Thor <author@example.com>\nX"
+	) >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'pretty format %(trailers:separator,key_value_separator) changes both separators' '
+	git log --no-walk --pretty=format:"%(trailers:separator=%x00,key_value_separator=%x00%x00,unfold)" >actual &&
+	(
+		printf "Signed-off-by\0\0A U Thor <author@example.com>\0" &&
+		printf "Acked-by\0\0A U Thor <author@example.com>\0" &&
+		printf "[ v2 updated patch description ]\0" &&
+		printf "Signed-off-by\0\0A U Thor <author@example.com>"
+	) >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'pretty format %(trailers) combining separator/key/keyonly/valueonly' '
 	git commit --allow-empty -F - <<-\EOF &&
 	Important fix
diff --git a/trailer.c b/trailer.c
index da95e1f3c66..70a560647c1 100644
--- a/trailer.c
+++ b/trailer.c
@@ -1233,8 +1233,12 @@ static void format_trailer_info(struct strbuf *out,
 					strbuf_addbuf(out, opts->separator);
 				if (!opts->value_only)
 					strbuf_addstr(out, tok.buf);
-				if (!opts->key_only && !opts->value_only)
-					strbuf_addstr(out, ": ");
+				if (!opts->key_only && !opts->value_only) {
+					if (opts->key_value_separator)
+						strbuf_addbuf(out, opts->key_value_separator);
+					else
+						strbuf_addstr(out, ": ");
+				}
 				if (!opts->key_only)
 					strbuf_addbuf(out, &val);
 				if (!opts->separator)
-- 
2.29.2.222.g5d2a92d10f8