Fix submodule dirty states not showing if submodules comes before files, or…

Fix submodule dirty states not showing if submodules comes before files, or there are only dirty submodules but no changed files

GIT_DIFF_PATCH_DIFFABLE was not set, so the diff content was not shown

When submodule is dirty, the hash may be the same, but the length is different because -dirty is appended

We can therefore compare the length or hash

src/diff_output.c

@@ -678,7 +678,8 @@ cleanup:
 		if ((delta->flags & GIT_DIFF_FLAG_BINARY) == 0 &&
 			delta->status != GIT_DELTA_UNMODIFIED &&
 			(patch->old_data.len || patch->new_data.len) &&
-			!git_oid_equal(&delta->old_file.oid, &delta->new_file.oid))
+			((patch->old_data.len != patch->new_data.len) ||
+				!git_oid_equal(&delta->old_file.oid, &delta->new_file.oid)))
 			patch->flags |= GIT_DIFF_PATCH_DIFFABLE;
 	}