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>

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;
@@ -723,14 +773,33 @@ 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;
 	}
 
 	/* normalize the log message to UTF-8. */
 	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;

t/t5100-mailinfo.sh

@@ -11,7 +11,7 @@ test_expect_success 'split sample box' \
 	'git mailsplit -o. "$TEST_DIRECTORY"/t5100/sample.mbox >last &&
 	last=`cat last` &&
 	echo total is $last &&
-	test `cat last` = 13'
+	test `cat last` = 14'
 
 for mail in `echo 00*`
 do

t/t5100/info0014

@@ -0,0 +1,5 @@
+Author: Junio C Hamano
+Email: gitster@pobox.com
+Subject: Teach mailinfo to ignore everything before -- >8 -- mark
+Date: Thu, 20 Aug 2009 17:18:22 -0700
+

t/t5100/msg0014

@@ -0,0 +1,4 @@
+This teaches mailinfo the scissors -- >8 -- mark; the command ignores
+everything before it in the message body.
+
+Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5100/patch0014

@@ -0,0 +1,64 @@
+---
+ builtin-mailinfo.c |   37 ++++++++++++++++++++++++++++++++++++-
+ 1 files changed, 36 insertions(+), 1 deletions(-)
+
+diff --git a/builtin-mailinfo.c b/builtin-mailinfo.c
+index b0b5d8f..461c47e 100644
+--- a/builtin-mailinfo.c
++++ b/builtin-mailinfo.c
+@@ -712,6 +712,34 @@ static inline int patchbreak(const struct strbuf *line)
+ 	return 0;
+ }
+
++static int scissors(const struct strbuf *line)
++{
++	size_t i, len = line->len;
++	int scissors_dashes_seen = 0;
++	const char *buf = line->buf;
++
++	for (i = 0; i < len; i++) {
++		if (isspace(buf[i]))
++			continue;
++		if (buf[i] == '-') {
++			scissors_dashes_seen |= 02;
++			continue;
++		}
++		if (i + 1 < len && !memcmp(buf + i, ">8", 2)) {
++			scissors_dashes_seen |= 01;
++			i++;
++			continue;
++		}
++		if (i + 7 < len && !memcmp(buf + i, "cut here", 8)) {
++			i += 7;
++			continue;
++		}
++		/* everything else --- not scissors */
++		break;
++	}
++	return scissors_dashes_seen == 03;
++}
++
+ static int handle_commit_msg(struct strbuf *line)
+ {
+ 	static int still_looking = 1;
+@@ -723,10 +751,17 @@ 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;
+ 	}
+
++	if (scissors(line)) {
++		fseek(cmitmsg, 0L, SEEK_SET);
++		still_looking = 1;
++		return 0;
++	}
++
+ 	/* normalize the log message to UTF-8. */
+ 	if (metainfo_charset)
+ 		convert_to_utf8(line, charset.buf);
+-- 
+1.6.4.1

t/t5100/sample.mbox

@@ -561,3 +561,92 @@ From: <a.u.thor@example.com> (A U Thor)
 Date: Fri, 9 Jun 2006 00:44:16 -0700
 Subject: [PATCH] a patch
 
+From nobody Mon Sep 17 00:00:00 2001
+From: Junio Hamano <junkio@cox.net>
+Date: Thu, 20 Aug 2009 17:18:22 -0700
+Subject: Why doesn't git-am does not like >8 scissors mark?
+
+Subject: [PATCH] BLAH ONE
+
+In real life, we will see a discussion that inspired this patch
+discussing related and unrelated things around >8 scissors mark
+in this part of the message.
+
+Subject: [PATCH] BLAH TWO
+
+And then we will see the scissors.
+
+ This line is not a scissors mark -- >8 -- but talks about it.
+ - - >8 - - please remove everything above this line - - >8 - -
+
+Subject: [PATCH] Teach mailinfo to ignore everything before -- >8 -- mark
+From: Junio C Hamano <gitster@pobox.com>
+
+This teaches mailinfo the scissors -- >8 -- mark; the command ignores
+everything before it in the message body.
+
+Signed-off-by: Junio C Hamano <gitster@pobox.com>
+---
+ builtin-mailinfo.c |   37 ++++++++++++++++++++++++++++++++++++-
+ 1 files changed, 36 insertions(+), 1 deletions(-)
+
+diff --git a/builtin-mailinfo.c b/builtin-mailinfo.c
+index b0b5d8f..461c47e 100644
+--- a/builtin-mailinfo.c
++++ b/builtin-mailinfo.c
+@@ -712,6 +712,34 @@ static inline int patchbreak(const struct strbuf *line)
+ 	return 0;
+ }
+
++static int scissors(const struct strbuf *line)
++{
++	size_t i, len = line->len;
++	int scissors_dashes_seen = 0;
++	const char *buf = line->buf;
++
++	for (i = 0; i < len; i++) {
++		if (isspace(buf[i]))
++			continue;
++		if (buf[i] == '-') {
++			scissors_dashes_seen |= 02;
++			continue;
++		}
++		if (i + 1 < len && !memcmp(buf + i, ">8", 2)) {
++			scissors_dashes_seen |= 01;
++			i++;
++			continue;
++		}
++		if (i + 7 < len && !memcmp(buf + i, "cut here", 8)) {
++			i += 7;
++			continue;
++		}
++		/* everything else --- not scissors */
++		break;
++	}
++	return scissors_dashes_seen == 03;
++}
++
+ static int handle_commit_msg(struct strbuf *line)
+ {
+ 	static int still_looking = 1;
+@@ -723,10 +751,17 @@ 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;
+ 	}
+
++	if (scissors(line)) {
++		fseek(cmitmsg, 0L, SEEK_SET);
++		still_looking = 1;
++		return 0;
++	}
++
+ 	/* normalize the log message to UTF-8. */
+ 	if (metainfo_charset)
+ 		convert_to_utf8(line, charset.buf);
+-- 
+1.6.4.1