Merge branch 'generation-numbers-in--contains'

These two changes improve these commands:

	1. `git tag --contains`
	2. `git branch --contains`

For `git branch --contains` the improvement depends on the tips, so the
boost will not work for recent remote branches (where we haven't
initialized the commit yet) but will help reduce the cost of containment
queries for old branches.

Author: dscho

commit.c

@@ -1076,12 +1076,19 @@ int in_merge_bases_many(struct commit *commit, int nr_reference, struct commit *
 {
 	struct commit_list *bases;
 	int ret = 0, i;
+	uint32_t min_generation = GENERATION_NUMBER_UNDEF;
 
 	if (parse_commit(commit))
 		return ret;
-	for (i = 0; i < nr_reference; i++)
+	for (i = 0; i < nr_reference; i++) {
 		if (parse_commit(reference[i]))
 			return ret;
+		if (min_generation > reference[i]->generation)
+			min_generation = reference[i]->generation;
+	}
+
+	if (commit->generation > min_generation)
+		return 0;
 
 	bases = paint_down_to_common(commit, nr_reference, reference);
 	if (commit->object.flags & PARENT2)

ref-filter.c

@@ -1584,7 +1584,8 @@ static int in_commit_list(const struct commit_list *want, struct commit *c)
  */
 static enum contains_result contains_test(struct commit *candidate,
 					  const struct commit_list *want,
-					  struct contains_cache *cache)
+					  struct contains_cache *cache,
+					  uint32_t cutoff)
 {
 	enum contains_result *cached = contains_cache_at(cache, candidate);
 
@@ -1598,8 +1599,11 @@ static enum contains_result contains_test(struct commit *candidate,
 		return CONTAINS_YES;
 	}
 
-	/* Otherwise, we don't know; prepare to recurse */
 	parse_commit_or_die(candidate);
+
+	if (candidate->generation < cutoff)
+		return CONTAINS_NO;
+
 	return CONTAINS_UNKNOWN;
 }
 
@@ -1615,8 +1619,18 @@ static enum contains_result contains_tag_algo(struct commit *candidate,
 					      struct contains_cache *cache)
 {
 	struct contains_stack contains_stack = { 0, 0, NULL };
-	enum contains_result result = contains_test(candidate, want, cache);
+	enum contains_result result;
+	uint32_t cutoff = GENERATION_NUMBER_UNDEF;
+	const struct commit_list *p;
+
+	for (p = want; p; p = p->next) {
+		struct commit *c = p->item;
+		parse_commit_or_die(c);
+		if (c->generation < cutoff)
+			cutoff = c->generation;
+	}
 
+	result = contains_test(candidate, want, cache, cutoff);
 	if (result != CONTAINS_UNKNOWN)
 		return result;
 
@@ -1634,7 +1648,7 @@ static enum contains_result contains_tag_algo(struct commit *candidate,
 		 * If we just popped the stack, parents->item has been marked,
 		 * therefore contains_test will return a meaningful yes/no.
 		 */
-		else switch (contains_test(parents->item, want, cache)) {
+		else switch (contains_test(parents->item, want, cache, cutoff)) {
 		case CONTAINS_YES:
 			*contains_cache_at(cache, commit) = CONTAINS_YES;
 			contains_stack.nr--;
@@ -1648,7 +1662,7 @@ static enum contains_result contains_tag_algo(struct commit *candidate,
 		}
 	}
 	free(contains_stack.contains_stack);
-	return contains_test(candidate, want, cache);
+	return contains_test(candidate, want, cache, cutoff);
 }
 
 static int commit_contains(struct ref_filter *filter, struct commit *commit,