+static int unreachable(struct expire_reflog_cb *cb, struct commit *commit, unsigned char *sha1)
+{
+ /*
+ * We may or may not have the commit yet - if not, look it
+ * up using the supplied sha1.
+ */
+ if (!commit) {
+ if (is_null_sha1(sha1))
+ return 0;
+
+ commit = lookup_commit_reference_gently(sha1, 1);
+
+ /* Not a commit -- keep it */
+ if (!commit)
+ return 0;
+ }
+
+ /* Reachable from the current ref? Don't prune. */
+ if (in_merge_bases(commit, &cb->ref_commit, 1))
+ return 0;
+
+ /* We can't reach it - prune it. */
+ return 1;
+}
+