Teach mailinfo to ignore everything before -- >8 -- mark

This teaches mailinfo the scissors -- >8 -- mark; the command ignores
everything before it in the message body.

For lefties among us, we also support -- 8< -- ;-)

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 70 insertions, 1 deletions

diff --git a/builtin-mailinfo.c b/builtin-mailinfo.c
index 50326d911c..a6f6b123b4 100644
--- a/builtin-mailinfo.c
+++ b/builtin-mailinfo.c
@@ -712,6 +712,56 @@ static inline int patchbreak(const struct strbuf *line)
 	return 0;
 }
 
+static int is_scissors_line(const struct strbuf *line)
+{
+	size_t i, len = line->len;
+	int scissors = 0, gap = 0;
+	int first_nonblank = -1;
+	int last_nonblank = 0, visible, perforation = 0, in_perforation = 0;
+	const char *buf = line->buf;
+
+	for (i = 0; i < len; i++) {
+		if (isspace(buf[i])) {
+			if (in_perforation) {
+				perforation++;
+				gap++;
+			}
+			continue;
+		}
+		last_nonblank = i;
+		if (first_nonblank < 0)
+			first_nonblank = i;
+		if (buf[i] == '-') {
+			in_perforation = 1;
+			perforation++;
+			continue;
+		}
+		if (i + 1 < len &&
+		    (!memcmp(buf + i, ">8", 2) || !memcmp(buf + i, "8<", 2))) {
+			in_perforation = 1;
+			perforation += 2;
+			scissors += 2;
+			i++;
+			continue;
+		}
+		in_perforation = 0;
+	}
+
+	/*
+	 * The mark must be at least 8 bytes long (e.g. "-- >8 --").
+	 * Even though there can be arbitrary cruft on the same line
+	 * (e.g. "cut here"), in order to avoid misidentification, the
+	 * perforation must occupy more than a third of the visible
+	 * width of the line, and dashes and scissors must occupy more
+	 * than half of the perforation.
+	 */
+
+	visible = last_nonblank - first_nonblank + 1;
+	return (scissors && 8 <= visible &&
+		visible < perforation * 3 &&
+		gap * 2 < perforation);
+}
+
 static int handle_commit_msg(struct strbuf *line)
 {
 	static int still_looking = 1;
@@ -723,7 +773,8 @@ static int handle_commit_msg(struct strbuf *line)
 		strbuf_ltrim(line);
 		if (!line->len)
 			return 0;
-		if ((still_looking = check_header(line, s_hdr_data, 0)) != 0)
+		still_looking = check_header(line, s_hdr_data, 0);
+		if (still_looking)
 			return 0;
 	}
 
@@ -731,6 +782,24 @@ static int handle_commit_msg(struct strbuf *line)
 	if (metainfo_charset)
 		convert_to_utf8(line, charset.buf);
 
+	if (is_scissors_line(line)) {
+		int i;
+		rewind(cmitmsg);
+		ftruncate(fileno(cmitmsg), 0);
+		still_looking = 1;
+
+		/*
+		 * We may have already read "secondary headers"; purge
+		 * them to give ourselves a clean restart.
+		 */
+		for (i = 0; header[i]; i++) {
+			if (s_hdr_data[i])
+				strbuf_release(s_hdr_data[i]);
+			s_hdr_data[i] = NULL;
+		}
+		return 0;
+	}
+
 	if (patchbreak(line)) {
 		fclose(cmitmsg);
 		cmitmsg = NULL;