+static struct repository *open_submodule(const char *path)
+{
+ struct strbuf sb = STRBUF_INIT;
+ struct repository *out = xmalloc(sizeof(*out));
+
+ if (submodule_to_gitdir(&sb, path) || repo_init(out, sb.buf, NULL)) {
+ strbuf_release(&sb);
+ free(out);
+ return NULL;
+ }
+
+ /* Mark it as a submodule */
+ out->submodule_prefix = xstrdup(path);
+
+ strbuf_release(&sb);
+ return out;
+}
+
+/*
+ * Helper function to display the submodule header line prior to the full
+ * summary output.
+ *
+ * If it can locate the submodule git directory it will create a repository
+ * handle for the submodule and lookup both the left and right commits and
+ * put them into the left and right pointers.
+ */
+static void show_submodule_header(struct diff_options *o,
+ const char *path,