interpret-trailers: add an option to unfold values

The point of "--only-trailers" is to give a caller an output
that's easy for them to parse. Getting rid of the
non-trailer material helps, but we still may see more
complicated syntax like whitespace continuation. Let's add
an option to unfold any continuation, giving the output as a
single "key: value" line per trailer.

As a bonus, this could be used even without --only-trailers
to clean up unusual formatting in the incoming data.

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

1 files changed, 29 insertions, 0 deletions

diff --git a/trailer.c b/trailer.c
index 847417ef89..e63f432947 100644
--- a/trailer.c
+++ b/trailer.c
@@ -886,6 +886,33 @@ static int ends_with_blank_line(const char *buf, size_t len)
 	return is_blank_line(buf + ll);
 }
 
+static void unfold_value(struct strbuf *val)
+{
+	struct strbuf out = STRBUF_INIT;
+	size_t i;
+
+	strbuf_grow(&out, val->len);
+	i = 0;
+	while (i < val->len) {
+		char c = val->buf[i++];
+		if (c == '\n') {
+			/* Collapse continuation down to a single space. */
+			while (i < val->len && isspace(val->buf[i]))
+				i++;
+			strbuf_addch(&out, ' ');
+		} else {
+			strbuf_addch(&out, c);
+		}
+	}
+
+	/* Empty lines may have left us with whitespace cruft at the edges */
+	strbuf_trim(&out);
+
+	/* output goes back to val as if we modified it in-place */
+	strbuf_swap(&out, val);
+	strbuf_release(&out);
+}
+
 static int process_input_file(FILE *outfile,
 			      const char *str,
 			      struct list_head *head,
@@ -914,6 +941,8 @@ static int process_input_file(FILE *outfile,
 		if (separator_pos >= 1) {
 			parse_trailer(&tok, &val, NULL, trailer,
 				      separator_pos);
+			if (opts->unfold)
+				unfold_value(&val);
 			add_trailer_item(head,
 					 strbuf_detach(&tok, NULL),
 					 strbuf_detach(&val, NULL));