merge-recursive: refuse to merge binary files

[jc: cherry-picked 9f30855 from 'master']

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

merge-recursive.c

@@ -680,6 +680,12 @@ static int ll_xdl_merge(const struct ll_merge_driver *drv_unused,
 {
 	xpparam_t xpp;
 
+	if (buffer_is_binary(orig->ptr, orig->size) ||
+			buffer_is_binary(src1->ptr, src1->size) ||
+			buffer_is_binary(src2->ptr, src2->size))
+		return error("Cannot merge binary files: %s vs. %s\n",
+			name1, name2);
+
 	memset(&xpp, 0, sizeof(xpp));
 	return xdl_merge(orig,
 			 src1, name1,

t/t6024-recursive-merge.sh

@@ -81,4 +81,18 @@ EOF
 
 test_expect_success "virtual trees were processed" "git diff expect out"
 
+git reset --hard
+test_expect_success 'refuse to merge binary files' '
+	printf "\0" > binary-file &&
+	git add binary-file &&
+	git commit -m binary &&
+	git checkout G &&
+	printf "\0\0" > binary-file &&
+	git add binary-file &&
+	git commit -m binary2 &&
+	! git merge F > merge.out 2> merge.err &&
+	grep "Cannot merge binary files: HEAD:binary-file vs. F:binary-file" \
+		merge.err
+'
+
 test_done