+static int mark_redundant_parents(struct rev_info *revs, struct commit *commit)
+{
+ struct commit_list *h = reduce_heads(commit->parents);
+ int i = 0, marked = 0;
+ struct commit_list *po, *pn;
+
+ /* Want these for sanity-checking only */
+ int orig_cnt = commit_list_count(commit->parents);
+ int cnt = commit_list_count(h);
+
+ /*
+ * Not ready to remove items yet, just mark them for now, based
+ * on the output of reduce_heads(). reduce_heads outputs the reduced
+ * set in its original order, so this isn't too hard.
+ */
+ po = commit->parents;
+ pn = h;
+ while (po) {
+ if (pn && po->item == pn->item) {
+ pn = pn->next;
+ i++;
+ } else {
+ po->item->object.flags |= TMP_MARK;
+ marked++;
+ }
+ po=po->next;
+ }
+
+ if (i != cnt || cnt+marked != orig_cnt)
+ die("mark_redundant_parents %d %d %d %d", orig_cnt, cnt, i, marked);
+
+ free_commit_list(h);
+
+ return marked;
+}
+
+static int mark_treesame_root_parents(struct rev_info *revs, struct commit *commit)
+{
+ struct commit_list *p;
+ int marked = 0;
+
+ for (p = commit->parents; p; p = p->next) {
+ struct commit *parent = p->item;
+ if (!parent->parents && (parent->object.flags & TREESAME)) {
+ parent->object.flags |= TMP_MARK;
+ marked++;
+ }
+ }
+
+ return marked;
+}
+
+/*
+ * Awkward naming - this means one parent we are TREESAME to.
+ * cf mark_treesame_root_parents: root parents that are TREESAME (to an
+ * empty tree). Better name suggestions?
+ */
+static int leave_one_treesame_to_parent(struct rev_info *revs, struct commit *commit)
+{
+ struct treesame_state *ts = lookup_decoration(&revs->treesame, &commit->object);
+ struct commit *unmarked = NULL, *marked = NULL;
+ struct commit_list *p;
+ unsigned n;
+
+ for (p = commit->parents, n = 0; p; p = p->next, n++) {
+ if (ts->treesame[n]) {
+ if (p->item->object.flags & TMP_MARK) {
+ if (!marked)
+ marked = p->item;
+ } else {
+ if (!unmarked) {
+ unmarked = p->item;
+ break;
+ }
+ }
+ }
+ }
+
+ /*
+ * If we are TREESAME to a marked-for-deletion parent, but not to any
+ * unmarked parents, unmark the first TREESAME parent. This is the
+ * parent that the default simplify_history==1 scan would have followed,
+ * and it doesn't make sense to omit that path when asking for a
+ * simplified full history. Retaining it improves the chances of
+ * understanding odd missed merges that took an old version of a file.
+ *
+ * Example:
+ *
+ * I--------*X A modified the file, but mainline merge X used
+ * \ / "-s ours", so took the version from I. X is
+ * `-*A--' TREESAME to I and !TREESAME to A.
+ *
+ * Default log from X would produce "I". Without this check,
+ * --full-history --simplify-merges would produce "I-A-X", showing
+ * the merge commit X and that it changed A, but not making clear that
+ * it had just taken the I version. With this check, the topology above
+ * is retained.
+ *
+ * Note that it is possible that the simplification chooses a different
+ * TREESAME parent from the default, in which case this test doesn't
+ * activate, and we _do_ drop the default parent. Example:
+ *
+ * I------X A modified the file, but it was reverted in B,
+ * \ / meaning mainline merge X is TREESAME to both
+ * *A-*B parents.
+ *
+ * Default log would produce "I" by following the first parent;
+ * --full-history --simplify-merges will produce "I-A-B". But this is a
+ * reasonable result - it presents a logical full history leading from
+ * I to X, and X is not an important merge.
+ */
+ if (!unmarked && marked) {
+ marked->object.flags &= ~TMP_MARK;
+ return 1;
+ }
+
+ return 0;
+}
+
+static int remove_marked_parents(struct rev_info *revs, struct commit *commit)
+{
+ struct commit_list **pp, *p;
+ int nth_parent, removed = 0;
+
+ pp = &commit->parents;
+ nth_parent = 0;
+ while ((p = *pp) != NULL) {
+ struct commit *parent = p->item;
+ if (parent->object.flags & TMP_MARK) {
+ parent->object.flags &= ~TMP_MARK;
+ *pp = p->next;
+ free(p);
+ removed++;
+ compact_treesame(revs, commit, nth_parent);
+ continue;
+ }
+ pp = &p->next;
+ nth_parent++;
+ }
+
+ /* Removing parents can only increase TREESAMEness */
+ if (removed && !(commit->object.flags & TREESAME))
+ update_treesame(revs, commit);
+
+ return nth_parent;
+}
+