+static void mark_edges_uninteresting(struct commit_list *list)
+{
+ for ( ; list; list = list->next) {
+ struct commit_list *parents = list->item->parents;
+
+ for ( ; parents; parents = parents->next) {
+ struct commit *commit = parents->item;
+ if (commit->object.flags & UNINTERESTING)
+ mark_tree_uninteresting(commit->tree);
+ }
+ }
+}
+
+static int is_different = 0;
+
+static void file_add_remove(struct diff_options *options,
+ int addremove, unsigned mode,
+ const unsigned char *sha1,
+ const char *base, const char *path)
+{
+ is_different = 1;
+}
+
+static void file_change(struct diff_options *options,
+ unsigned old_mode, unsigned new_mode,
+ const unsigned char *old_sha1,
+ const unsigned char *new_sha1,
+ const char *base, const char *path)
+{
+ is_different = 1;
+}
+
+static struct diff_options diff_opt = {
+ .recursive = 1,
+ .add_remove = file_add_remove,
+ .change = file_change,
+};
+
+static int same_tree(struct tree *t1, struct tree *t2)
+{
+ is_different = 0;
+ if (diff_tree_sha1(t1->object.sha1, t2->object.sha1, "", &diff_opt) < 0)
+ return 0;
+ return !is_different;
+}
+
+static int same_tree_as_empty(struct tree *t1)
+{
+ int retval;
+ void *tree;
+ struct tree_desc empty, real;
+
+ if (!t1)
+ return 0;
+
+ tree = read_object_with_reference(t1->object.sha1, "tree", &real.size, NULL);
+ if (!tree)
+ return 0;
+ real.buf = tree;
+
+ empty.buf = "";
+ empty.size = 0;
+
+ is_different = 0;
+ retval = diff_tree(&empty, &real, "", &diff_opt);
+ free(tree);
+
+ return retval >= 0 && !is_different;
+}
+
+static struct commit *try_to_simplify_merge(struct commit *commit, struct commit_list *parent)
+{
+ if (!commit->tree)
+ return NULL;
+
+ while (parent) {
+ struct commit *p = parent->item;
+ parent = parent->next;
+ parse_commit(p);
+ if (!p->tree)
+ continue;
+ if (same_tree(commit->tree, p->tree))
+ return p;
+ }
+ return NULL;
+}
+
+static void add_parents_to_list(struct commit *commit, struct commit_list **list)
+{
+ struct commit_list *parent = commit->parents;
+
+ /*
+ * If the commit is uninteresting, don't try to
+ * prune parents - we want the maximal uninteresting
+ * set.
+ *
+ * Normally we haven't parsed the parent
+ * yet, so we won't have a parent of a parent
+ * here. However, it may turn out that we've
+ * reached this commit some other way (where it
+ * wasn't uninteresting), in which case we need
+ * to mark its parents recursively too..
+ */
+ if (commit->object.flags & UNINTERESTING) {
+ while (parent) {
+ struct commit *p = parent->item;
+ parent = parent->next;
+ parse_commit(p);
+ p->object.flags |= UNINTERESTING;
+ if (p->parents)
+ mark_parents_uninteresting(p);
+ if (p->object.flags & SEEN)
+ continue;
+ p->object.flags |= SEEN;
+ insert_by_date(p, list);
+ }
+ return;
+ }
+
+ /*
+ * Ok, the commit wasn't uninteresting. If it
+ * is a merge, try to find the parent that has
+ * no differences in the path set if one exists.
+ */
+ if (paths && parent && parent->next) {
+ struct commit *preferred;
+
+ preferred = try_to_simplify_merge(commit, parent);
+ if (preferred) {
+ parent->item = preferred;
+ parent->next = NULL;
+ }
+ }
+
+ while (parent) {
+ struct commit *p = parent->item;
+
+ parent = parent->next;
+
+ parse_commit(p);
+ if (p->object.flags & SEEN)
+ continue;
+ p->object.flags |= SEEN;
+ insert_by_date(p, list);
+ }
+}
+
+static void compress_list(struct commit_list *list)
+{
+ while (list) {
+ struct commit *commit = list->item;
+ struct commit_list *parent = commit->parents;
+ list = list->next;
+
+ if (!parent) {
+ if (!same_tree_as_empty(commit->tree))
+ commit->object.flags |= TREECHANGE;
+ continue;
+ }
+
+ /*
+ * Exactly one parent? Check if it leaves the tree
+ * unchanged
+ */
+ if (!parent->next) {
+ struct tree *t1 = commit->tree;
+ struct tree *t2 = parent->item->tree;
+ if (!t1 || !t2 || same_tree(t1, t2))
+ continue;
+ }
+ commit->object.flags |= TREECHANGE;
+ }
+}
+
+static struct commit_list *limit_list(struct commit_list *list)