+/**
+ * Returns 1 if the index differs from HEAD, 0 otherwise. When on an unborn
+ * branch, returns 1 if there are entries in the index, 0 otherwise. If an
+ * strbuf is provided, the space-separated list of files that differ will be
+ * appended to it.
+ */
+static int index_has_changes(struct strbuf *sb)
+{
+ unsigned char head[GIT_SHA1_RAWSZ];
+ int i;
+
+ if (!get_sha1_tree("HEAD", head)) {
+ struct diff_options opt;
+
+ diff_setup(&opt);
+ DIFF_OPT_SET(&opt, EXIT_WITH_STATUS);
+ if (!sb)
+ DIFF_OPT_SET(&opt, QUICK);
+ do_diff_cache(head, &opt);
+ diffcore_std(&opt);
+ for (i = 0; sb && i < diff_queued_diff.nr; i++) {
+ if (i)
+ strbuf_addch(sb, ' ');
+ strbuf_addstr(sb, diff_queued_diff.queue[i]->two->path);
+ }
+ diff_flush(&opt);
+ return DIFF_OPT_TST(&opt, HAS_CHANGES) != 0;
+ } else {
+ for (i = 0; sb && i < active_nr; i++) {
+ if (i)
+ strbuf_addch(sb, ' ');
+ strbuf_addstr(sb, active_cache[i]->name);
+ }
+ return !!active_nr;
+ }
+}
+