[PATCH] format-patch: escape "From " lines recognized by mailsplit

[Eric Wong <e@80x24.org>]

Users have mistakenly copied "From " lines into commit messages
in the past, and will certainly make the same mistakes in the
future.  Since not everyone uses mboxrd, yet, we should at least
prevent miss-split mails by always escaping "From " lines based
on the check used by mailsplit.

mailsplit will not perform unescaping by default, yet, as it
could cause further invocations of format-patch from old
versions of git to generate bad output.  Propagating the mboxo
escaping is preferable to miss-split patches.  Unescaping may
still be performed via "--mboxrd".

ref: https://public-inbox.org/git/20160606230248.GA15906@dcvr.yhbt.net/T/#u

Signed-off-by: Eric Wong <e@80x24.org>
---
 builtin/mailsplit.c     | 32 +-------------------------------
 mailinfo.c              | 31 +++++++++++++++++++++++++++++++
 mailinfo.h              |  1 +
 pretty.c                | 16 +++++++++++++---
 t/t4014-format-patch.sh | 14 ++++++++++++++
 5 files changed, 60 insertions(+), 34 deletions(-)

diff --git a/builtin/mailsplit.c b/builtin/mailsplit.c
index 3068168..bb8f9c9 100644
--- a/builtin/mailsplit.c
+++ b/builtin/mailsplit.c
@@ -8,41 +8,11 @@
 #include "builtin.h"
 #include "string-list.h"
 #include "strbuf.h"
+#include "mailinfo.h"
 
 static const char git_mailsplit_usage[] =
 "git mailsplit [-d<prec>] [-f<n>] [-b] [--keep-cr] -o<directory> [(<mbox>|<Maildir>)...]";
 
-static int is_from_line(const char *line, int len)
-{
-	const char *colon;
-
-	if (len < 20 || memcmp("From ", line, 5))
-		return 0;
-
-	colon = line + len - 2;
-	line += 5;
-	for (;;) {
-		if (colon < line)
-			return 0;
-		if (*--colon == ':')
-			break;
-	}
-
-	if (!isdigit(colon[-4]) ||
-	    !isdigit(colon[-2]) ||
-	    !isdigit(colon[-1]) ||
-	    !isdigit(colon[ 1]) ||
-	    !isdigit(colon[ 2]))
-		return 0;
-
-	/* year */
-	if (strtol(colon+3, NULL, 10) <= 90)
-		return 0;
-
-	/* Ok, close enough */
-	return 1;
-}
-
 static struct strbuf buf = STRBUF_INIT;
 static int keep_cr;
 static int mboxrd;
diff --git a/mailinfo.c b/mailinfo.c
index 9f19ca1..0ebd953 100644
--- a/mailinfo.c
+++ b/mailinfo.c
@@ -1035,3 +1035,34 @@ void clear_mailinfo(struct mailinfo *mi)
 
 	strbuf_release(&mi->log_message);
 }
+
+int is_from_line(const char *line, int len)
+{
+	const char *colon;
+
+	if (len < 20 || memcmp("From ", line, 5))
+		return 0;
+
+	colon = line + len - 2;
+	line += 5;
+	for (;;) {
+		if (colon < line)
+			return 0;
+		if (*--colon == ':')
+			break;
+	}
+
+	if (!isdigit(colon[-4]) ||
+	    !isdigit(colon[-2]) ||
+	    !isdigit(colon[-1]) ||
+	    !isdigit(colon[ 1]) ||
+	    !isdigit(colon[ 2]))
+		return 0;
+
+	/* year */
+	if (strtol(colon+3, NULL, 10) <= 90)
+		return 0;
+
+	/* Ok, close enough */
+	return 1;
+}
diff --git a/mailinfo.h b/mailinfo.h
index 93776a7..c1430a0 100644
--- a/mailinfo.h
+++ b/mailinfo.h
@@ -37,5 +37,6 @@ struct mailinfo {
 extern void setup_mailinfo(struct mailinfo *);
 extern int mailinfo(struct mailinfo *, const char *msg, const char *patch);
 extern void clear_mailinfo(struct mailinfo *);
+int is_from_line(const char *line, int len);
 
 #endif /* MAILINFO_H */
diff --git a/pretty.c b/pretty.c
index 9fa42c2..898c0a3 100644
--- a/pretty.c
+++ b/pretty.c
@@ -10,6 +10,7 @@
 #include "color.h"
 #include "reflog-walk.h"
 #include "gpg-interface.h"
+#include "mailinfo.h"
 
 static char *user_format;
 static struct cmt_fmt_map {
@@ -1745,9 +1746,18 @@ void pp_remainder(struct pretty_print_context *pp,
 			strbuf_add_tabexpand(sb, pp->expand_tabs_in_log,
 					     line, linelen);
 		else {
-			if (pp->fmt == CMIT_FMT_MBOXRD &&
-					is_mboxrd_from(line, linelen))
-				strbuf_addch(sb, '>');
+			switch (pp->fmt) {
+			case CMIT_FMT_EMAIL:
+				if (is_from_line(line, linelen))
+					strbuf_addch(sb, '>');
+				break;
+			case CMIT_FMT_MBOXRD:
+				if (is_mboxrd_from(line, linelen))
+					strbuf_addch(sb, '>');
+				break;
+			default:
+				break;
+			}
 
 			strbuf_add(sb, line, linelen);
 		}
diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
index 1206c48..8fa3982 100755
--- a/t/t4014-format-patch.sh
+++ b/t/t4014-format-patch.sh
@@ -1606,4 +1606,18 @@ test_expect_success 'format-patch --pretty=mboxrd' '
 	test_cmp expect actual
 '
 
+test_expect_success 'format-patch From escaping' '
+	cat >msg <<-INPUT_END &&
+	somebody pasted format-patch output into a body
+
+	From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+	INPUT_END
+
+	C=$(git commit-tree HEAD^^{tree} -p HEAD <msg) &&
+	git format-patch --stdout -1 $C~1..$C >patch &&
+	git grep -h --no-index \
+		">From 0000000000000000000000000000000000000000 " \
+		patch
+'
+
 test_done
-- 
EW