+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 (commit->object.flags & REACHABLE)
+ return 0;
+ if (in_merge_bases(commit, &cb->ref_commit, 1))
+ return 0;
+
+ /* We can't reach it - prune it. */
+ return 1;
+}
+
+static void mark_reachable(struct commit *commit, unsigned long expire_limit)
+{
+ /*
+ * We need to compute whether the commit on either side of a reflog
+ * entry is reachable from the tip of the ref for all entries.
+ * Mark commits that are reachable from the tip down to the
+ * time threshold first; we know a commit marked thusly is
+ * reachable from the tip without running in_merge_bases()
+ * at all.
+ */
+ struct commit_list *pending = NULL;
+
+ commit_list_insert(commit, &pending);
+ while (pending) {
+ struct commit_list *entry = pending;
+ struct commit_list *parent;
+ pending = entry->next;
+ commit = entry->item;
+ free(entry);
+ if (commit->object.flags & REACHABLE)
+ continue;
+ if (parse_commit(commit))
+ continue;
+ commit->object.flags |= REACHABLE;
+ if (commit->date < expire_limit)
+ continue;
+ parent = commit->parents;
+ while (parent) {
+ commit = parent->item;
+ parent = parent->next;
+ if (commit->object.flags & REACHABLE)
+ continue;
+ commit_list_insert(commit, &pending);
+ }
+ }
+}
+