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()

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 &&