pretty: add merge and exclude options to %(describe)

Allow restricting the tags used by the placeholder %(describe) with the
options match and exclude.  E.g. the following command describes the
current commit using official version tags, without those for release
candidates:

   $ git log -1 --format='%(describe:match=v[0-9]*,exclude=*rc*)'

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 41 insertions, 2 deletions

diff --git a/pretty.c b/pretty.c
index a0c427fb61..c612d2ac9b 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1150,6 +1150,34 @@ static int format_trailer_match_cb(const struct strbuf *key, void *ud)
 	return 0;
 }
 
+static size_t parse_describe_args(const char *start, struct strvec *args)
+{
+	const char *options[] = { "match", "exclude" };
+	const char *arg = start;
+
+	for (;;) {
+		const char *matched = NULL;
+		const char *argval;
+		size_t arglen = 0;
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(options); i++) {
+			if (match_placeholder_arg_value(arg, options[i], &arg,
+							&argval, &arglen)) {
+				matched = options[i];
+				break;
+			}
+		}
+		if (!matched)
+			break;
+
+		if (!arglen)
+			return 0;
+		strvec_pushf(args, "--%s=%.*s", matched, (int)arglen, argval);
+	}
+	return arg - start;
+}
+
 static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 				const char *placeholder,
 				void *context)
@@ -1215,20 +1243,31 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 		return parse_padding_placeholder(placeholder, c);
 	}
 
-	if (skip_prefix(placeholder, "(describe)", &arg)) {
+	if (skip_prefix(placeholder, "(describe", &arg)) {
 		struct child_process cmd = CHILD_PROCESS_INIT;
 		struct strbuf out = STRBUF_INIT;
 		struct strbuf err = STRBUF_INIT;
 
 		cmd.git_cmd = 1;
 		strvec_push(&cmd.args, "describe");
+
+		if (*arg == ':') {
+			arg++;
+			arg += parse_describe_args(arg, &cmd.args);
+		}
+
+		if (*arg != ')') {
+			child_process_clear(&cmd);
+			return 0;
+		}
+
 		strvec_push(&cmd.args, oid_to_hex(&commit->object.oid));
 		pipe_command(&cmd, NULL, 0, &out, 0, &err, 0);
 		strbuf_rtrim(&out);
 		strbuf_addbuf(sb, &out);
 		strbuf_release(&out);
 		strbuf_release(&err);
-		return arg - placeholder;
+		return arg - placeholder + 1;
 	}
 
 	/* these depend on the commit */