interpret-trailers: add an option to show only existing trailers

It can be useful to invoke interpret-trailers for the
primary purpose of parsing existing trailers. But in that
case, we don't want to apply existing ifMissing or ifExists
rules from the config. Let's add a special mode where we
avoid applying those rules. Coupled with --only-trailers,
this gives us a reasonable parsing tool.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/trailer.c b/trailer.c
index 83225c6828..847417ef89 100644
--- a/trailer.c
+++ b/trailer.c
@@ -976,7 +976,6 @@ void process_trailers(const char *file,
 		      struct string_list *trailers)
 {
 	LIST_HEAD(head);
-	LIST_HEAD(arg_head);
 	struct strbuf sb = STRBUF_INIT;
 	int trailer_end;
 	FILE *outfile = stdout;
@@ -991,9 +990,11 @@ void process_trailers(const char *file,
 	/* Print the lines before the trailers */
 	trailer_end = process_input_file(outfile, sb.buf, &head, opts);
 
-	process_command_line_args(&arg_head, trailers);
-
-	process_trailers_lists(&head, &arg_head);
+	if (!opts->only_input) {
+		LIST_HEAD(arg_head);
+		process_command_line_args(&arg_head, trailers);
+		process_trailers_lists(&head, &arg_head);
+	}
 
 	print_all(outfile, &head, opts);