[PATCH 1/2] mailsplit: Remove any '>' characters used to escape From_ lines in mbox.

@@ -46,6 +46,30 @@ static int is_from_line(const char *line, int len)
 static struct strbuf buf = STRBUF_INIT;
 static int keep_cr;
 
+/* Write the line in 'buf' to 'output', but if we are splitting an mbox,
+ * then remove the first '>' from any line that begins with one or more
+ * '>' characters followed by "From ".
+ *
+ * Return 0 if successful, 1 for any write error.
+ */
+static int write_buf_unescaping(FILE *output, int is_mbox)
+{
+	const char *line = buf.buf;
+	size_t len = buf.len;
+
+	if (is_mbox && *line == '>') {
+		const char *s = line;
+		while (*s == '>')
+			s++;
+		if (strncmp (s, "From ", 5) == 0) {
+			line = line + 1;
+			len = len - 1;
+		}
+	}
+
+	return fwrite(line, 1, len, output) != len;
+}
+
 /* Called with the first line (potentially partial)
  * already in buf[] -- normally that should begin with
  * the Unix "From " line.  Write it into the specified

@@ -76,7 +100,7 @@ static int split_one(FILE *mbox, const char *name, int allow_bare)
 			strbuf_addch(&buf, '\n');
 		}
 
-		if (fwrite(buf.buf, 1, buf.len, output) != buf.len)
+		if (write_buf_unescaping(output, !is_bare))
 			die_errno("cannot write output");
 
 		if (strbuf_getwholeline(&buf, mbox, '\n')) {

@@ -0,0 +1,64 @@
+#!/bin/sh
+
+test_description='git am properly unescaping From_ lines'
+
+. ./test-lib.sh
+
+cat >msg <<EOF
+From_ lines
+
+This is a commit message that contains a From_ line, which is line
+that begins with the characters "From ". Get ready for it, now...
+From this time forward, we'll have no From_-line bugs.
+
+Additionally, we'll also test lines that are escaped versions of From_
+lines. These are lines that begin with one or more '>' characters that
+are then followed by the characters "From ". We want to ensure that
+none of these intentional '>' characters get swallowed. Let's try that
+with three variations, (with 1, 2, and 3 leading '>' characters):
+
+>From now on (with one leading '>')
+>>From there to here (with two leading '>' characters)
+>>>From Here to Eternity (with three leading '>' characters)
+
+EOF
+
+test_expect_success setup '
+	echo hello >file &&
+	git add file &&
+	test_tick &&
+	git commit -m first &&
+	git tag first &&
+	echo world >>file &&
+	git add file &&
+	test_tick &&
+	git commit -s -F msg &&
+	git tag second &&
+	git format-patch --stdout first | sed -e "1{p;d};s/^\(>*From \)/>\1/" > From_ &&
+	{
+		echo "X-Fake-Field: Line One" &&
+		echo "X-Fake-Field: Line Two" &&
+		echo "X-Fake-Field: Line Three" &&
+		git format-patch --stdout first | sed -e "1d"
+	} > From_.eml
+'
+
+test_expect_success 'am unescapes From_ lines from mbox' '
+	git checkout first &&
+	git am From_ &&
+	! test -d .git/rebase-apply &&
+	test -z "$(git diff second)" &&
+	test "$(git rev-parse second)" = "$(git rev-parse HEAD)" &&
+	test "$(git rev-parse second^)" = "$(git rev-parse HEAD^)"
+'
+
+test_expect_success 'am does not unescape From_ lines from email' '
+	git checkout first &&
+	git am From_.eml &&
+	! test -d .git/rebase-apply &&
+	test -z "$(git diff second)" &&
+	test "$(git rev-parse second)" = "$(git rev-parse HEAD)" &&
+	test "$(git rev-parse second^)" = "$(git rev-parse HEAD^)"
+'
+
+test_done