mailsplit: support unescaping mboxrd messages

This will allow us to parse the output of --pretty=mboxrd
and the output of other mboxrd generators.

Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-mailsplit.txt

@@ -8,7 +8,8 @@ git-mailsplit - Simple UNIX mbox splitter program
 SYNOPSIS
 --------
 [verse]
-'git mailsplit' [-b] [-f<nn>] [-d<prec>] [--keep-cr] -o<directory> [--] [(<mbox>|<Maildir>)...]
+'git mailsplit' [-b] [-f<nn>] [-d<prec>] [--keep-cr] [--mboxrd]
+		-o<directory> [--] [(<mbox>|<Maildir>)...]
 
 DESCRIPTION
 -----------
@@ -47,6 +48,10 @@ OPTIONS
 --keep-cr::
 	Do not remove `\r` from lines ending with `\r\n`.
 
+--mboxrd::
+	Input is of the "mboxrd" format and "^>+From " line escaping is
+	reversed.
+
 GIT
 ---
 Part of the linkgit:git[1] suite

builtin/mailsplit.c

@@ -45,6 +45,19 @@ static int is_from_line(const char *line, int len)
 
 static struct strbuf buf = STRBUF_INIT;
 static int keep_cr;
+static int mboxrd;
+
+static int is_gtfrom(const struct strbuf *buf)
+{
+	size_t min = strlen(">From ");
+	size_t ngt;
+
+	if (buf->len < min)
+		return 0;
+
+	ngt = strspn(buf->buf, ">");
+	return ngt && starts_with(buf->buf + ngt, "From ");
+}
 
 /* Called with the first line (potentially partial)
  * already in buf[] -- normally that should begin with
@@ -77,6 +90,9 @@ static int split_one(FILE *mbox, const char *name, int allow_bare)
 			strbuf_addch(&buf, '\n');
 		}
 
+		if (mboxrd && is_gtfrom(&buf))
+			strbuf_remove(&buf, 0, 1);
+
 		if (fwrite(buf.buf, 1, buf.len, output) != buf.len)
 			die_errno("cannot write output");
 
@@ -271,6 +287,8 @@ int cmd_mailsplit(int argc, const char **argv, const char *prefix)
 			keep_cr = 1;
 		} else if ( arg[1] == 'o' && arg[2] ) {
 			dir = arg+2;
+		} else if (!strcmp(arg, "--mboxrd")) {
+			mboxrd = 1;
 		} else if ( arg[1] == '-' && !arg[2] ) {
 			argp++;	/* -- marks end of options */
 			break;

t/t5100-mailinfo.sh

@@ -111,4 +111,35 @@ test_expect_success 'mailinfo on message with quoted >From' '
 	test_cmp "$TEST_DIRECTORY"/t5100/quoted-from.expect quoted-from/msg
 '
 
+test_expect_success 'mailinfo unescapes with --mboxrd' '
+	mkdir mboxrd &&
+	git mailsplit -omboxrd --mboxrd \
+		"$TEST_DIRECTORY"/t5100/sample.mboxrd >last &&
+	test x"$(cat last)" = x2 &&
+	for i in 0001 0002
+	do
+		git mailinfo mboxrd/msg mboxrd/patch \
+		  <mboxrd/$i >mboxrd/out &&
+		test_cmp "$TEST_DIRECTORY"/t5100/${i}mboxrd mboxrd/msg
+	done &&
+	sp=" " &&
+	echo "From " >expect &&
+	echo "From " >>expect &&
+	echo >> expect &&
+	cat >sp <<-INPUT_END &&
+	From mboxrd Mon Sep 17 00:00:00 2001
+	From: trailing spacer <sp@example.com>
+	Subject: [PATCH] a commit with trailing space
+
+	From$sp
+	>From$sp
+
+	INPUT_END
+
+	git mailsplit -f2 -omboxrd --mboxrd <sp >last &&
+	test x"$(cat last)" = x1 &&
+	git mailinfo mboxrd/msg mboxrd/patch <mboxrd/0003 &&
+	test_cmp expect mboxrd/msg
+'
+
 test_done

t/t5100/0001mboxrd

@@ -0,0 +1,4 @@
+From the beginning, mbox should have been mboxrd
+>From escaped
+From not mangled but this line should have been escaped
+

t/t5100/0002mboxrd

@@ -0,0 +1,5 @@
+ >From unchanged
+ From also unchanged
+no trailing space, no escaping necessary and '>' was intended:
+>From
+

t/t5100/sample.mboxrd

@@ -0,0 +1,19 @@
+From mboxrd Mon Sep 17 00:00:00 2001
+From: mboxrd writer <mboxrd@example.com>
+Date: Fri, 9 Jun 2006 00:44:16 -0700
+Subject: [PATCH] a commit with escaped From lines
+
+>From the beginning, mbox should have been mboxrd
+>>From escaped
+From not mangled but this line should have been escaped
+
+From mboxrd Mon Sep 17 00:00:00 2001
+From: mboxrd writer <mboxrd@example.com>
+Date: Fri, 9 Jun 2006 00:44:16 -0700
+Subject: [PATCH 2/2] another with fake From lines
+
+ >From unchanged
+ From also unchanged
+no trailing space, no escaping necessary and '>' was intended:
+>From
+