Merge branch 'tc/last-modified-bloom' into seen

The 'git last-modified' command has been optimized by using Bloom
filters.  It now reuses revision walk filtering logic from 'git log'
to pre-filter commits, and maintains per-path Bloom filters even when
wildcard pathspecs are used.

* tc/last-modified-bloom:
  last-modified: keep per-path Bloom filters for wildcard pathspecs
  last-modified: check pathspec against Bloom filter first
  revision: expose check for paths maybe changed in Bloom filter
  revision: move bloom keyvec precondition into function

builtin/last-modified.c

@@ -272,6 +272,9 @@ static bool maybe_changed_path(struct last_modified *lm,
 	if (!filter)
 		return true;
 
+	if (revs_maybe_changed_in_bloom(&lm->rev, filter) == 0)
+		return false;
+
 	hashmap_for_each_entry(&lm->paths, &iter, ent, hashent) {
 		if (active && !bitmap_get(active, ent->diff_idx))
 			continue;
@@ -358,6 +361,14 @@ static int last_modified_run(struct last_modified *lm)
 
 	prepare_revision_walk(&lm->rev);
 
+	/*
+	 * prepare_revision_walk() clears bloom_filter_settings for pathspecs
+	 * without a Bloom key. Restore it so the per-path check keeps working.
+	 */
+	if (!lm->rev.bloom_filter_settings)
+		lm->rev.bloom_filter_settings =
+			get_bloom_filter_settings(lm->rev.repo);
+
 	max_count = lm->rev.max_count;
 
 	init_active_paths_for_commit(&lm->active_paths);

revision.c

@@ -750,29 +750,43 @@ static int check_maybe_different_in_bloom_filter(struct rev_info *revs,
 						 struct commit *commit)
 {
 	struct bloom_filter *filter;
-	int result = 0;
+	int result;
 
 	if (commit_graph_generation(commit) == GENERATION_NUMBER_INFINITY)
 		return -1;
 
 	filter = get_bloom_filter(revs->repo, commit);
-
 	if (!filter) {
 		count_bloom_filter_not_present++;
 		return -1;
 	}
 
+	result = revs_maybe_changed_in_bloom(revs, filter);
+	if (result < 0)
+		return result;
+
+	if (result)
+		count_bloom_filter_maybe++;
+	else
+		count_bloom_filter_definitely_not++;
+
+	return result;
+}
+
+int revs_maybe_changed_in_bloom(struct rev_info *revs,
+				struct bloom_filter *filter)
+{
+	int result = 0;
+
+	if (!revs->bloom_keyvecs_nr)
+		return -1;
+
 	for (size_t nr = 0; !result && nr < revs->bloom_keyvecs_nr; nr++) {
 		result = bloom_filter_contains_vec(filter,
 						   revs->bloom_keyvecs[nr],
 						   revs->bloom_filter_settings);
 	}
 
-	if (result)
-		count_bloom_filter_maybe++;
-	else
-		count_bloom_filter_definitely_not++;
-
 	return result;
 }
 
@@ -806,7 +820,7 @@ static int rev_compare_tree(struct rev_info *revs,
 			return REV_TREE_SAME;
 	}
 
-	if (revs->bloom_keyvecs_nr && !nth_parent) {
+	if (!nth_parent) {
 		bloom_ret = check_maybe_different_in_bloom_filter(revs, commit);
 
 		if (bloom_ret == 0)
@@ -833,7 +847,7 @@ static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit,
 	if (!t1)
 		return 0;
 
-	if (!nth_parent && revs->bloom_keyvecs_nr) {
+	if (!nth_parent) {
 		bloom_ret = check_maybe_different_in_bloom_filter(revs, commit);
 		if (!bloom_ret)
 			return 1;

revision.h

@@ -68,6 +68,7 @@ struct string_list;
 struct saved_parents;
 struct follow_pathspec_slab;
 struct bloom_keyvec;
+struct bloom_filter;
 struct bloom_filter_settings;
 struct option;
 struct parse_opt_ctx_t;
@@ -495,6 +496,22 @@ void reset_revision_walk(void);
  */
 int prepare_revision_walk(struct rev_info *revs);
 
+/**
+ * Take in a changed-path Bloom filter that belongs to a commit, and consult it
+ * to see if it might have modified any of the paths in the `revs`.
+ * The caller should look up `filter`, probably with get_bloom_filter().
+ * prepare_revision_walk() needs to be called in advance to ensure
+ * pathspec key vectors are set up.
+ *
+ * Returns -1 if no sensible answer could be given because of missing
+ * preconditions (no pathspec key vectors).
+ * Returns 0 if the commit definitely did not change any of the paths and 1 if
+ * the commit maybe has changed one of them, although that might be a
+ * false-positive.
+ */
+int revs_maybe_changed_in_bloom(struct rev_info *revs,
+				struct bloom_filter *filter);
+
 /* Drain the commits linked list into the priority queue. */
 void rev_info_commit_list_to_queue(struct rev_info *revs);
 /**