Merge branch 'jk/log-decorate-optim'

Optimize "git log" for cases where we wasted cycles to load ref
decoration data that may not be needed.

* jk/log-decorate-optim:
  load_ref_decorations(): fix decoration with tags
  add_ref_decoration(): rename s/type/deco_type/
  load_ref_decorations(): avoid parsing non-tag objects
  object.h: add lookup_object_by_type() function
  object.h: expand docstring for lookup_unknown_object()
  log: avoid loading decorations for userformats that don't need it
  pretty.h: update and expand docstring for userformat_find_requirements()

8 files changed, 77 insertions, 32 deletions

diff --git a/builtin/log.c b/builtin/log.c
index 516a1142dd..3d7717ba5c 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -245,6 +245,9 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 			rev->abbrev_commit = 0;
 	}
 
+	if (rev->commit_format == CMIT_FMT_USERFORMAT && !w.decorate)
+		decoration_style = 0;
+
 	if (decoration_style) {
 		const struct string_list *config_exclude =
 			repo_config_get_value_multi(the_repository,
diff --git a/log-tree.c b/log-tree.c
index 7b823786c2..6dc4412268 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -134,7 +134,8 @@ static int add_ref_decoration(const char *refname, const struct object_id *oid,
 			      int flags, void *cb_data)
 {
 	struct object *obj;
-	enum decoration_type type = DECORATION_NONE;
+	enum object_type objtype;
+	enum decoration_type deco_type = DECORATION_NONE;
 	struct decoration_filter *filter = (struct decoration_filter *)cb_data;
 
 	if (filter && !ref_filter_match(refname, filter))
@@ -155,28 +156,29 @@ static int add_ref_decoration(const char *refname, const struct object_id *oid,
 		return 0;
 	}
 
-	obj = parse_object(the_repository, oid);
-	if (!obj)
+	objtype = oid_object_info(the_repository, oid, NULL);
+	if (objtype < 0)
 		return 0;
+	obj = lookup_object_by_type(the_repository, oid, objtype);
 
 	if (starts_with(refname, "refs/heads/"))
-		type = DECORATION_REF_LOCAL;
+		deco_type = DECORATION_REF_LOCAL;
 	else if (starts_with(refname, "refs/remotes/"))
-		type = DECORATION_REF_REMOTE;
+		deco_type = DECORATION_REF_REMOTE;
 	else if (starts_with(refname, "refs/tags/"))
-		type = DECORATION_REF_TAG;
+		deco_type = DECORATION_REF_TAG;
 	else if (!strcmp(refname, "refs/stash"))
-		type = DECORATION_REF_STASH;
+		deco_type = DECORATION_REF_STASH;
 	else if (!strcmp(refname, "HEAD"))
-		type = DECORATION_REF_HEAD;
+		deco_type = DECORATION_REF_HEAD;
 
-	add_name_decoration(type, refname, obj);
+	add_name_decoration(deco_type, refname, obj);
 	while (obj->type == OBJ_TAG) {
+		if (!obj->parsed)
+			parse_object(the_repository, &obj->oid);
 		obj = ((struct tag *)obj)->tagged;
 		if (!obj)
 			break;
-		if (!obj->parsed)
-			parse_object(the_repository, &obj->oid);
 		add_name_decoration(DECORATION_REF_TAG, refname, obj);
 	}
 	return 0;
diff --git a/object.c b/object.c
index 2b3c075a15..4e85955a94 100644
--- a/object.c
+++ b/object.c
@@ -185,6 +185,24 @@ struct object *lookup_unknown_object(struct repository *r, const struct object_i
 	return obj;
 }
 
+struct object *lookup_object_by_type(struct repository *r,
+			    const struct object_id *oid,
+			    enum object_type type)
+{
+	switch (type) {
+	case OBJ_COMMIT:
+		return (struct object *)lookup_commit(r, oid);
+	case OBJ_TREE:
+		return (struct object *)lookup_tree(r, oid);
+	case OBJ_TAG:
+		return (struct object *)lookup_tag(r, oid);
+	case OBJ_BLOB:
+		return (struct object *)lookup_blob(r, oid);
+	default:
+		die("BUG: unknown object type %d", type);
+	}
+}
+
 struct object *parse_object_buffer(struct repository *r, const struct object_id *oid, enum object_type type, unsigned long size, void *buffer, int *eaten_p)
 {
 	struct object *obj;
diff --git a/object.h b/object.h
index 8bca310713..3b38c9cc98 100644
--- a/object.h
+++ b/object.h
@@ -144,9 +144,27 @@ struct object *parse_object_or_die(const struct object_id *oid, const char *name
  */
 struct object *parse_object_buffer(struct repository *r, const struct object_id *oid, enum object_type type, unsigned long size, void *buffer, int *eaten_p);
 
-/** Returns the object, with potentially excess memory allocated. **/
+/*
+ * Allocate and return an object struct, even if you do not know the type of
+ * the object. The returned object may have its "type" field set to a real type
+ * (if somebody previously called lookup_blob(), etc), or it may be set to
+ * OBJ_NONE. In the latter case, subsequent calls to lookup_blob(), etc, will
+ * set the type field as appropriate.
+ *
+ * Use this when you do not know the expected type of an object and want to
+ * avoid parsing it for efficiency reasons. Try to avoid it otherwise; it
+ * may allocate excess memory, since the returned object must be as large as
+ * the maximum struct of any type.
+ */
 struct object *lookup_unknown_object(struct repository *r, const struct object_id *oid);
 
+/*
+ * Dispatch to the appropriate lookup_blob(), lookup_commit(), etc, based on
+ * "type".
+ */
+struct object *lookup_object_by_type(struct repository *r, const struct object_id *oid,
+				     enum object_type type);
+
 struct object_list *object_list_insert(struct object *item,
 				       struct object_list **list_p);
 
diff --git a/pretty.c b/pretty.c
index b1ecd039ce..9631529c10 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1735,6 +1735,10 @@ static size_t userformat_want_item(struct strbuf *sb, const char *placeholder,
 	case 'S':
 		w->source = 1;
 		break;
+	case 'd':
+	case 'D':
+		w->decorate = 1;
+		break;
 	}
 	return 0;
 }
diff --git a/pretty.h b/pretty.h
index f034609e4d..2f16acd213 100644
--- a/pretty.h
+++ b/pretty.h
@@ -65,12 +65,16 @@ static inline int cmit_fmt_is_mail(enum cmit_fmt fmt)
 	return (fmt == CMIT_FMT_EMAIL || fmt == CMIT_FMT_MBOXRD);
 }
 
+/*
+ * Examine the user-specified format given by "fmt" (or if NULL, the global one
+ * previously saved by get_commit_format()), and set flags based on which items
+ * the format will need when it is expanded.
+ */
 struct userformat_want {
 	unsigned notes:1;
 	unsigned source:1;
+	unsigned decorate:1;
 };
-
-/* Set the flag "w->notes" if there is placeholder %N in "fmt". */
 void userformat_find_requirements(const char *fmt, struct userformat_want *w);
 
 /*
diff --git a/reachable.c b/reachable.c
index c59847257a..84e3d0d75e 100644
--- a/reachable.c
+++ b/reachable.c
@@ -159,24 +159,6 @@ int add_unseen_recent_objects_to_traversal(struct rev_info *revs,
 				      FOR_EACH_OBJECT_LOCAL_ONLY);
 }
 
-static void *lookup_object_by_type(struct repository *r,
-				   const struct object_id *oid,
-				   enum object_type type)
-{
-	switch (type) {
-	case OBJ_COMMIT:
-		return lookup_commit(r, oid);
-	case OBJ_TREE:
-		return lookup_tree(r, oid);
-	case OBJ_TAG:
-		return lookup_tag(r, oid);
-	case OBJ_BLOB:
-		return lookup_blob(r, oid);
-	default:
-		die("BUG: unknown object type %d", type);
-	}
-}
-
 static int mark_object_seen(const struct object_id *oid,
 			     enum object_type type,
 			     int exclude,
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index 39e746fbcb..9dfead936b 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -1915,6 +1915,20 @@ test_expect_success '--exclude-promisor-objects does not BUG-crash' '
 	test_must_fail git log --exclude-promisor-objects source-a
 '
 
+test_expect_success 'log --decorate includes all levels of tag annotated tags' '
+	git checkout -b branch &&
+	git commit --allow-empty -m "new commit" &&
+	git tag lightweight HEAD &&
+	git tag -m annotated annotated HEAD &&
+	git tag -m double-0 double-0 HEAD &&
+	git tag -m double-1 double-1 double-0 &&
+	cat >expect <<-\EOF &&
+	HEAD -> branch, tag: lightweight, tag: double-1, tag: double-0, tag: annotated
+	EOF
+	git log -1 --format="%D" >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'log --end-of-options' '
        git update-ref refs/heads/--source HEAD &&
        git log --end-of-options --source >actual &&