+static int is_submodule_commit_present(const char *path, unsigned char sha1[20])
+{
+ int is_present = 0;
+ if (!add_submodule_odb(path) && lookup_commit_reference(sha1)) {
+ /* Even if the submodule is checked out and the commit is
+ * present, make sure it is reachable from a ref. */
+ struct child_process cp;
+ const char *argv[] = {"rev-list", "-n", "1", NULL, "--not", "--all", NULL};
+ struct strbuf buf = STRBUF_INIT;
+
+ argv[3] = sha1_to_hex(sha1);
+ memset(&cp, 0, sizeof(cp));
+ cp.argv = argv;
+ cp.env = local_repo_env;
+ cp.git_cmd = 1;
+ cp.no_stdin = 1;
+ cp.out = -1;
+ cp.dir = path;
+ if (!run_command(&cp) && !strbuf_read(&buf, cp.out, 1024))
+ is_present = 1;
+
+ close(cp.out);
+ strbuf_release(&buf);
+ }
+ return is_present;
+}
+
+static void submodule_collect_changed_cb(struct diff_queue_struct *q,
+ struct diff_options *options,
+ void *data)
+{
+ int i;
+ for (i = 0; i < q->nr; i++) {
+ struct diff_filepair *p = q->queue[i];
+ if (!S_ISGITLINK(p->two->mode))
+ continue;
+
+ if (S_ISGITLINK(p->one->mode)) {
+ /* NEEDSWORK: We should honor the name configured in
+ * the .gitmodules file of the commit we are examining
+ * here to be able to correctly follow submodules
+ * being moved around. */
+ struct string_list_item *path;
+ path = unsorted_string_list_lookup(&changed_submodule_paths, p->two->path);
+ if (!path && !is_submodule_commit_present(p->two->path, p->two->sha1))
+ string_list_append(&changed_submodule_paths, xstrdup(p->two->path));
+ } else {
+ /* Submodule is new or was moved here */
+ /* NEEDSWORK: When the .git directories of submodules
+ * live inside the superprojects .git directory some
+ * day we should fetch new submodules directly into
+ * that location too when config or options request
+ * that so they can be checked out from there. */
+ continue;
+ }
+ }
+}
+
+void check_for_new_submodule_commits(unsigned char new_sha1[20])
+{
+ struct rev_info rev;
+ struct commit *commit;
+ const char *argv[] = {NULL, NULL, "--not", "--all", NULL};
+ int argc = ARRAY_SIZE(argv) - 1;
+
+ init_revisions(&rev, NULL);
+ argv[1] = xstrdup(sha1_to_hex(new_sha1));
+ setup_revisions(argc, argv, &rev, NULL);
+ if (prepare_revision_walk(&rev))
+ die("revision walk setup failed");
+
+ /*
+ * Collect all submodules (whether checked out or not) for which new
+ * commits have been recorded upstream in "changed_submodule_paths".
+ */
+ while ((commit = get_revision(&rev))) {
+ struct commit_list *parent = commit->parents;
+ while (parent) {
+ struct diff_options diff_opts;
+ diff_setup(&diff_opts);
+ diff_opts.output_format |= DIFF_FORMAT_CALLBACK;
+ diff_opts.format_callback = submodule_collect_changed_cb;
+ if (diff_setup_done(&diff_opts) < 0)
+ die("diff_setup_done failed");
+ diff_tree_sha1(parent->item->object.sha1, commit->object.sha1, "", &diff_opts);
+ diffcore_std(&diff_opts);
+ diff_flush(&diff_opts);
+ parent = parent->next;
+ }
+ }
+ free((char *)argv[1]);
+}
+