return 1;
}
+/*
+ * A definition of "relevant" commit that we can use to simplify limited graphs
+ * by eliminating side branches.
+ *
+ * A "relevant" commit is one that is !UNINTERESTING (ie we are including it
+ * in our list), or that is a specified BOTTOM commit. Then after computing
+ * a limited list, during processing we can generally ignore boundary merges
+ * coming from outside the graph, (ie from irrelevant parents), and treat
+ * those merges as if they were single-parent. TREESAME is defined to consider
+ * only relevant parents, if any. If we are TREESAME to our on-graph parents,
+ * we don't care if we were !TREESAME to non-graph parents.
+ *
+ * Treating bottom commits as relevant ensures that a limited graph's
+ * connection to the actual bottom commit is not viewed as a side branch, but
+ * treated as part of the graph. For example:
+ *
+ * ....Z...A---X---o---o---B
+ * . /
+ * W---Y
+ *
+ * When computing "A..B", the A-X connection is at least as important as
+ * Y-X, despite A being flagged UNINTERESTING.
+ *
+ * And when computing --ancestry-path "A..B", the A-X connection is more
+ * important than Y-X, despite both A and Y being flagged UNINTERESTING.
+ */
+static inline int relevant_commit(struct commit *commit)
+{
+ return (commit->object.flags & (UNINTERESTING | BOTTOM)) != UNINTERESTING;
+}
+
+/*
+ * Return a single relevant commit from a parent list. If we are a TREESAME
+ * commit, and this selects one of our parents, then we can safely simplify to
+ * that parent.
+ */
+static struct commit *one_relevant_parent(const struct rev_info *revs,
+ struct commit_list *orig)
+{
+ struct commit_list *list = orig;
+ struct commit *relevant = NULL;
+
+ if (!orig)
+ return NULL;
+
+ /*
+ * For 1-parent commits, or if first-parent-only, then return that
+ * first parent (even if not "relevant" by the above definition).
+ * TREESAME will have been set purely on that parent.
+ */
+ if (revs->first_parent_only || !orig->next)
+ return orig->item;
+
+ /*
+ * For multi-parent commits, identify a sole relevant parent, if any.
+ * If we have only one relevant parent, then TREESAME will be set purely
+ * with regard to that parent, and we can simplify accordingly.
+ *
+ * If we have more than one relevant parent, or no relevant parents
+ * (and multiple irrelevant ones), then we can't select a parent here
+ * and return NULL.
+ */
+ while (list) {
+ struct commit *commit = list->item;
+ list = list->next;
+ if (relevant_commit(commit)) {
+ if (relevant)
+ return NULL;
+ relevant = commit;
+ }
+ }
+ return relevant;
+}
+
/*
* The goal is to get REV_TREE_NEW as the result only if the
* diff consists of all '+' (and no other changes), REV_TREE_OLD
if (commit->parents && commit->parents->next) {
unsigned n;
struct treesame_state *st;
+ struct commit_list *p;
+ unsigned relevant_parents;
+ unsigned relevant_change, irrelevant_change;
st = lookup_decoration(&revs->treesame, &commit->object);
if (!st)
die("update_treesame %s", sha1_to_hex(commit->object.sha1));
- commit->object.flags |= TREESAME;
- for (n = 0; n < st->nparents; n++) {
- if (!st->treesame[n]) {
- commit->object.flags &= ~TREESAME;
- break;
- }
+ relevant_parents = 0;
+ relevant_change = irrelevant_change = 0;
+ for (p = commit->parents, n = 0; p; n++, p = p->next) {
+ if (relevant_commit(p->item)) {
+ relevant_change |= !st->treesame[n];
+ relevant_parents++;
+ } else
+ irrelevant_change |= !st->treesame[n];
}
+ if (relevant_parents ? relevant_change : irrelevant_change)
+ commit->object.flags &= ~TREESAME;
+ else
+ commit->object.flags |= TREESAME;
}
return commit->object.flags & TREESAME;
}
+static inline int limiting_can_increase_treesame(const struct rev_info *revs)
+{
+ /*
+ * TREESAME is irrelevant unless prune && dense;
+ * if simplify_history is set, we can't have a mixture of TREESAME and
+ * !TREESAME INTERESTING parents (and we don't have treesame[]
+ * decoration anyway);
+ * if first_parent_only is set, then the TREESAME flag is locked
+ * against the first parent (and again we lack treesame[] decoration).
+ */
+ return revs->prune && revs->dense &&
+ !revs->simplify_history &&
+ !revs->first_parent_only;
+}
+
static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
{
struct commit_list **pp, *parent;
struct treesame_state *ts = NULL;
- int tree_changed = 0, nth_parent;
+ int relevant_change = 0, irrelevant_change = 0;
+ int relevant_parents, nth_parent;
/*
* If we don't do pruning, everything is interesting
if (!revs->dense && !commit->parents->next)
return;
- for (pp = &commit->parents, nth_parent = 0;
+ for (pp = &commit->parents, nth_parent = 0, relevant_parents = 0;
(parent = *pp) != NULL;
pp = &parent->next, nth_parent++) {
struct commit *p = parent->item;
+ if (relevant_commit(p))
+ relevant_parents++;
if (nth_parent == 1) {
/*
!revs->simplify_history &&
!(commit->object.flags & UNINTERESTING)) {
ts = initialise_treesame(revs, commit);
- if (!tree_changed)
+ if (!(irrelevant_change || relevant_change))
ts->treesame[0] = 1;
}
}
/* fallthrough */
case REV_TREE_OLD:
case REV_TREE_DIFFERENT:
- tree_changed = 1;
+ if (relevant_commit(p))
+ relevant_change = 1;
+ else
+ irrelevant_change = 1;
continue;
}
die("bad tree compare for commit %s", sha1_to_hex(commit->object.sha1));
}
- if (tree_changed)
- return;
- commit->object.flags |= TREESAME;
+
+ /*
+ * TREESAME is straightforward for single-parent commits. For merge
+ * commits, it is most useful to define it so that "irrelevant"
+ * parents cannot make us !TREESAME - if we have any relevant
+ * parents, then we only consider TREESAMEness with respect to them,
+ * allowing irrelevant merges from uninteresting branches to be
+ * simplified away. Only if we have only irrelevant parents do we
+ * base TREESAME on them. Note that this logic is replicated in
+ * update_treesame, which should be kept in sync.
+ */
+ if (relevant_parents ? !relevant_change : !irrelevant_change)
+ commit->object.flags |= TREESAME;
}
static void commit_list_insert_by_date_cached(struct commit *p, struct commit_list **head,
free_commit_list(bottom);
}
+ /*
+ * Check if any commits have become TREESAME by some of their parents
+ * becoming UNINTERESTING.
+ */
+ if (limiting_can_increase_treesame(revs))
+ for (list = newlist; list; list = list->next) {
+ struct commit *c = list->item;
+ if (c->object.flags & (UNINTERESTING | TREESAME))
+ continue;
+ update_treesame(revs, c);
+ }
+
revs->commits = newlist;
return 0;
}
static struct commit_list **simplify_one(struct rev_info *revs, struct commit *commit, struct commit_list **tail)
{
struct commit_list *p;
+ struct commit *parent;
struct merge_simplify_state *st, *pst;
int cnt;
/*
* A commit simplifies to itself if it is a root, if it is
* UNINTERESTING, if it touches the given paths, or if it is a
- * merge and its parents simplify to more than one commit
+ * merge and its parents don't simplify to one relevant commit
* (the first two cases are already handled at the beginning of
* this function).
*
- * Otherwise, it simplifies to what its sole parent simplifies to.
+ * Otherwise, it simplifies to what its sole relevant parent
+ * simplifies to.
*/
if (!cnt ||
(commit->object.flags & UNINTERESTING) ||
!(commit->object.flags & TREESAME) ||
- (1 < cnt))
+ (parent = one_relevant_parent(revs, commit->parents)) == NULL)
st->simplified = commit;
else {
- pst = locate_simplify_state(revs, commit->parents->item);
+ pst = locate_simplify_state(revs, parent);
st->simplified = pst->simplified;
}
return tail;
free(list);
/* Signal whether we need per-parent treesame decoration */
- if (revs->simplify_merges)
+ if (revs->simplify_merges ||
+ (revs->limited && limiting_can_increase_treesame(revs)))
revs->treesame.name = "treesame";
if (revs->no_walk != REVISION_WALK_NO_WALK_UNSORTED)
if (!revs->limited)
if (add_parents_to_list(revs, p, &revs->commits, &cache) < 0)
return rewrite_one_error;
- if (p->parents && p->parents->next)
- return rewrite_one_ok;
if (p->object.flags & UNINTERESTING)
return rewrite_one_ok;
if (!(p->object.flags & TREESAME))
return rewrite_one_ok;
if (!p->parents)
return rewrite_one_noparents;
- *pp = p->parents->item;
+ if ((p = one_relevant_parent(revs, p->parents)) == NULL)
+ return rewrite_one_ok;
+ *pp = p;
}
}