rerere forget: grok files containing NUL

Using 'git rerere forget .' after a merge that involved binary files
runs into an infinite loop if the binary file contains a zero byte.
Replace a strchrnul by memchr because the former does not make progress
as soon as the NUL is encountered.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

rerere.c

@@ -284,8 +284,10 @@ static int rerere_mem_getline(struct strbuf *sb, struct rerere_io *io_)
 	strbuf_release(sb);
 	if (!io->input.len)
 		return -1;
-	ep = strchrnul(io->input.buf, '\n');
-	if (*ep == '\n')
+	ep = memchr(io->input.buf, '\n', io->input.len);
+	if (!ep)
+		ep = io->input.buf + io->input.len;
+	else if (*ep == '\n')
 		ep++;
 	len = ep - io->input.buf;
 	strbuf_add(sb, io->input.buf, len);

t/t2030-unresolve-info.sh

@@ -44,9 +44,13 @@ prime_resolve_undo () {
 
 test_expect_success setup '
 	mkdir fi &&
+	printf "a\0a" >binary &&
+	git add binary &&
 	test_commit initial fi/le first &&
 	git branch side &&
 	git branch another &&
+	printf "a\0b" >binary &&
+	git add binary &&
 	test_commit second fi/le second &&
 	git checkout side &&
 	test_commit third fi/le third &&
@@ -167,4 +171,12 @@ test_expect_success 'rerere and rerere forget (subdirectory)' '
 	test_cmp expect actual
 '
 
+test_expect_success 'rerere forget (binary)' '
+	git checkout -f side &&
+	printf "a\0c" >binary &&
+	git commit -a -m binary &&
+	test_must_fail git merge second &&
+	git rerere forget binary
+'
+
 test_done