Merge branch 'en/batch-prefetch'

In a lazy clone, "git cherry" and "git grep" often fetch necessary
blob objects one by one from promisor remotes.  It has been corrected
to collect necessary object names and fetch them in bulk to gain
reasonable performance.

* en/batch-prefetch:
  grep: prefetch necessary blobs
  builtin/log: prefetch necessary blobs for `git cherry`
  patch-ids.h: add missing trailing parenthesis in documentation comment
  promisor-remote: document caller filtering contract

builtin/grep.c

@@ -28,9 +28,12 @@
 #include "object-file.h"
 #include "object-name.h"
 #include "odb.h"
+#include "oid-array.h"
+#include "oidset.h"
 #include "packfile.h"
 #include "pager.h"
 #include "path.h"
+#include "promisor-remote.h"
 #include "read-cache-ll.h"
 #include "write-or-die.h"
 
@@ -692,6 +695,144 @@ static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
 	return hit;
 }
 
+static void collect_blob_oids_for_tree(struct repository *repo,
+				       const struct pathspec *pathspec,
+				       struct tree_desc *tree,
+				       struct strbuf *base,
+				       int tn_len,
+				       struct oidset *blob_oids)
+{
+	struct name_entry entry;
+	int old_baselen = base->len;
+	struct strbuf name = STRBUF_INIT;
+	enum interesting match = entry_not_interesting;
+
+	while (tree_entry(tree, &entry)) {
+		if (match != all_entries_interesting) {
+			strbuf_addstr(&name, base->buf + tn_len);
+			match = tree_entry_interesting(repo->index,
+						       &entry, &name,
+						       pathspec);
+			strbuf_reset(&name);
+
+			if (match == all_entries_not_interesting)
+				break;
+			if (match == entry_not_interesting)
+				continue;
+		}
+
+		strbuf_add(base, entry.path, tree_entry_len(&entry));
+
+		if (S_ISREG(entry.mode)) {
+			if (!odb_has_object(repo->objects, &entry.oid, 0))
+				oidset_insert(blob_oids, &entry.oid);
+		} else if (S_ISDIR(entry.mode)) {
+			enum object_type type;
+			struct tree_desc sub_tree;
+			void *data;
+			unsigned long size;
+
+			data = odb_read_object(repo->objects, &entry.oid,
+					       &type, &size);
+			if (!data)
+				die(_("unable to read tree (%s)"),
+				    oid_to_hex(&entry.oid));
+
+			strbuf_addch(base, '/');
+			init_tree_desc(&sub_tree, &entry.oid, data, size);
+			collect_blob_oids_for_tree(repo, pathspec, &sub_tree,
+						   base, tn_len, blob_oids);
+			free(data);
+		}
+		/*
+		 * ...no else clause for S_ISGITLINK: submodules have their
+		 * own promisor configuration and would need separate fetches
+		 * anyway.
+		 */
+
+		strbuf_setlen(base, old_baselen);
+	}
+
+	strbuf_release(&name);
+}
+
+static void collect_blob_oids_for_treeish(struct grep_opt *opt,
+					  const struct pathspec *pathspec,
+					  const struct object_id *tree_ish_oid,
+					  const char *name,
+					  struct oidset *blob_oids)
+{
+	struct tree_desc tree;
+	void *data;
+	unsigned long size;
+	struct strbuf base = STRBUF_INIT;
+	int len;
+
+	data = odb_read_object_peeled(opt->repo->objects, tree_ish_oid,
+				      OBJ_TREE, &size, NULL);
+
+	if (!data)
+		return;
+
+	len = name ? strlen(name) : 0;
+	if (len) {
+		strbuf_add(&base, name, len);
+		strbuf_addch(&base, ':');
+	}
+	init_tree_desc(&tree, tree_ish_oid, data, size);
+
+	collect_blob_oids_for_tree(opt->repo, pathspec, &tree,
+				   &base, base.len, blob_oids);
+
+	strbuf_release(&base);
+	free(data);
+}
+
+static void prefetch_grep_blobs(struct grep_opt *opt,
+				const struct pathspec *pathspec,
+				const struct object_array *list)
+{
+	struct oidset blob_oids = OIDSET_INIT;
+
+	/* Exit if we're not in a partial clone */
+	if (!repo_has_promisor_remote(opt->repo))
+		return;
+
+	/* For each tree, gather the blobs in it */
+	for (int i = 0; i < list->nr; i++) {
+		struct object *real_obj;
+
+		obj_read_lock();
+		real_obj = deref_tag(opt->repo, list->objects[i].item,
+				     NULL, 0);
+		obj_read_unlock();
+
+		if (real_obj &&
+		    (real_obj->type == OBJ_COMMIT ||
+		     real_obj->type == OBJ_TREE))
+			collect_blob_oids_for_treeish(opt, pathspec,
+						      &real_obj->oid,
+						      list->objects[i].name,
+						      &blob_oids);
+	}
+
+	/* Prefetch the blobs we found */
+	if (oidset_size(&blob_oids)) {
+		struct oid_array to_fetch = OID_ARRAY_INIT;
+		struct oidset_iter iter;
+		const struct object_id *oid;
+
+		oidset_iter_init(&blob_oids, &iter);
+		while ((oid = oidset_iter_next(&iter)))
+			oid_array_append(&to_fetch, oid);
+
+		promisor_remote_get_direct(opt->repo, to_fetch.oid, to_fetch.nr);
+
+		oid_array_clear(&to_fetch);
+	}
+	oidset_clear(&blob_oids);
+}
+
 static int grep_object(struct grep_opt *opt, const struct pathspec *pathspec,
 		       struct object *obj, const char *name, const char *path)
 {
@@ -732,6 +873,8 @@ static int grep_objects(struct grep_opt *opt, const struct pathspec *pathspec,
 	int hit = 0;
 	const unsigned int nr = list->nr;
 
+	prefetch_grep_blobs(opt, pathspec, list);
+
 	for (i = 0; i < nr; i++) {
 		struct object *real_obj;
 

builtin/log.c

@@ -21,10 +21,12 @@
 #include "color.h"
 #include "commit.h"
 #include "diff.h"
+#include "diffcore.h"
 #include "diff-merges.h"
 #include "revision.h"
 #include "log-tree.h"
 #include "oid-array.h"
+#include "oidset.h"
 #include "tag.h"
 #include "reflog-walk.h"
 #include "patch-ids.h"
@@ -43,9 +45,11 @@
 #include "utf8.h"
 
 #include "commit-reach.h"
+#include "promisor-remote.h"
 #include "range-diff.h"
 #include "tmp-objdir.h"
 #include "tree.h"
+#include "userdiff.h"
 #include "write-or-die.h"
 
 #define MAIL_DEFAULT_WRAP 72
@@ -2602,6 +2606,131 @@ static void print_commit(char sign, struct commit *commit, int verbose,
 	}
 }
 
+/*
+ * Enumerate blob OIDs from a single commit's diff, inserting them into blobs.
+ * Skips files whose userdiff driver explicitly declares binary status
+ * (drv->binary > 0), since patch-ID uses oid_to_hex() for those and
+ * never reads blob content.  Use userdiff_find_by_path() since
+ * diff_filespec_load_driver() is static in diff.c.
+ *
+ * Clean up with diff_queue_clear() (from diffcore.h).
+ */
+static void collect_diff_blob_oids(struct commit *commit,
+				   struct diff_options *opts,
+				   struct oidset *blobs)
+{
+	struct diff_queue_struct *q;
+
+	/*
+	 * Merge commits are filtered out by patch_id_defined() in patch-ids.c,
+	 * so we'll never be called with one.
+	 */
+	assert(!commit->parents || !commit->parents->next);
+
+	if (commit->parents)
+		diff_tree_oid(&commit->parents->item->object.oid,
+			      &commit->object.oid, "", opts);
+	else
+		diff_root_tree_oid(&commit->object.oid, "", opts);
+	diffcore_std(opts);
+
+	q = &diff_queued_diff;
+	for (int i = 0; i < q->nr; i++) {
+		struct diff_filepair *p = q->queue[i];
+		struct userdiff_driver *drv;
+
+		/* Skip binary files */
+		drv = userdiff_find_by_path(opts->repo->index, p->one->path);
+		if (drv && drv->binary > 0)
+			continue;
+
+		if (DIFF_FILE_VALID(p->one) &&
+		    odb_read_object_info_extended(opts->repo->objects,
+						  &p->one->oid, NULL,
+						  OBJECT_INFO_FOR_PREFETCH))
+			oidset_insert(blobs, &p->one->oid);
+		if (DIFF_FILE_VALID(p->two) &&
+		    odb_read_object_info_extended(opts->repo->objects,
+						  &p->two->oid, NULL,
+						  OBJECT_INFO_FOR_PREFETCH))
+			oidset_insert(blobs, &p->two->oid);
+	}
+	diff_queue_clear(q);
+}
+
+static int always_match(const void *cmp_data UNUSED,
+			const struct hashmap_entry *entry1 UNUSED,
+			const struct hashmap_entry *entry2 UNUSED,
+			const void *keydata UNUSED)
+{
+	return 0;
+}
+
+/*
+ * Prefetch blobs for git cherry in partial clones.
+ *
+ * Called between the revision walk (which builds the head-side
+ * commit list) and the has_commit_patch_id() comparison loop.
+ *
+ * Uses a cmpfn-swap trick to avoid reading blobs: temporarily
+ * replaces the hashmap's comparison function with a trivial
+ * always-match function, so hashmap_get()/hashmap_get_next() match
+ * any entry with the same oidhash bucket.  These are the set of oids
+ * that would trigger patch_id_neq() during normal lookup and cause
+ * blobs to be read on demand, and we want to prefetch them all at
+ * once instead.
+ */
+static void prefetch_cherry_blobs(struct repository *repo,
+				  struct commit_list *list,
+				  struct patch_ids *ids)
+{
+	struct oidset blobs = OIDSET_INIT;
+	hashmap_cmp_fn original_cmpfn;
+
+	/* Exit if we're not in a partial clone */
+	if (!repo_has_promisor_remote(repo))
+		return;
+
+	/* Save original cmpfn, replace with always_match */
+	original_cmpfn = ids->patches.cmpfn;
+	ids->patches.cmpfn = always_match;
+
+	/* Find header-only collisions, gather blobs from those commits */
+	for (struct commit_list *l = list; l; l = l->next) {
+		struct commit *c = l->item;
+		bool match_found = false;
+		for (struct patch_id *cur = patch_id_iter_first(c, ids);
+		     cur;
+		     cur = patch_id_iter_next(cur, ids)) {
+			match_found = true;
+			collect_diff_blob_oids(cur->commit, &ids->diffopts,
+					       &blobs);
+		}
+		if (match_found)
+			collect_diff_blob_oids(c, &ids->diffopts, &blobs);
+	}
+
+	/* Restore original cmpfn */
+	ids->patches.cmpfn = original_cmpfn;
+
+	/* If we have any blobs to fetch, fetch them */
+	if (oidset_size(&blobs)) {
+		struct oid_array to_fetch = OID_ARRAY_INIT;
+		struct oidset_iter iter;
+		const struct object_id *oid;
+
+		oidset_iter_init(&blobs, &iter);
+		while ((oid = oidset_iter_next(&iter)))
+			oid_array_append(&to_fetch, oid);
+
+		promisor_remote_get_direct(repo, to_fetch.oid, to_fetch.nr);
+
+		oid_array_clear(&to_fetch);
+	}
+
+	oidset_clear(&blobs);
+}
+
 int cmd_cherry(int argc,
 	       const char **argv,
 	       const char *prefix,
@@ -2673,6 +2802,8 @@ int cmd_cherry(int argc,
 		commit_list_insert(commit, &list);
 	}
 
+	prefetch_cherry_blobs(the_repository, list, &ids);
+
 	for (struct commit_list *l = list; l; l = l->next) {
 		char sign = '+';