patch_parse: reject empty path names

When parsing patch headers, we currently accept empty path names just
fine, e.g. a line "--- \n" would be parsed as the empty filename. This
is not a valid patch format and may cause `NULL` pointer accesses at a
later place as `git_buf_detach` will return `NULL` in that case.

Reject such patches as malformed with a nice error message.

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/patch/parse.c b/tests/patch/parse.c
index fb185eb2a..ede5a96e2 100644
--- a/tests/patch/parse.c
+++ b/tests/patch/parse.c
@@ -149,6 +149,13 @@ void test_patch_parse__lifetime_of_patch_does_not_depend_on_buffer(void)
 	git_patch_free(patch);
 }
 
+void test_patch_parse__binary_file_with_missing_paths(void)
+{
+	git_patch *patch;
+	cl_git_fail(git_patch_from_buffer(&patch, PATCH_BINARY_FILE_WITH_MISSING_PATHS,
+					  strlen(PATCH_BINARY_FILE_WITH_MISSING_PATHS), NULL));
+}
+
 void test_patch_parse__memory_leak_on_multiple_paths(void)
 {
 	git_patch *patch;