log-tree: call load_ref_decorations() in get_name_decoration()

Load a default set of ref name decorations at the first lookup.  This
frees direct and indirect callers from doing so.  They can still do it
if they want to use a filter or are interested in full decorations
instead of the default short ones -- the first load_ref_decorations()
call wins.

This means that the load in builtin/log.c::cmd_log_init_finish() is
respected even if --simplify-by-decoration is given, as the previously
dominating earlier load in handle_revision_opt() is gone.  So a filter
given with --decorate-refs-exclude is used for simplification in that
case, as expected.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

log-tree.c

@@ -77,6 +77,7 @@ void add_name_decoration(enum decoration_type type, const char *name, struct obj
 
 const struct name_decoration *get_name_decoration(const struct object *obj)
 {
+	load_ref_decorations(NULL, DECORATE_SHORT_REFS);
 	return lookup_decoration(&name_decoration, obj);
 }
 

pretty.c

@@ -1239,11 +1239,9 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 		strbuf_addstr(sb, get_revision_mark(NULL, commit));
 		return 1;
 	case 'd':
-		load_ref_decorations(NULL, DECORATE_SHORT_REFS);
 		format_decorations(sb, commit, c->auto_color);
 		return 1;
 	case 'D':
-		load_ref_decorations(NULL, DECORATE_SHORT_REFS);
 		format_decorations_extended(sb, commit, c->auto_color, "", ", ", "");
 		return 1;
 	case 'S':		/* tag/branch like --source */

revision.c

@@ -2063,7 +2063,6 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->simplify_by_decoration = 1;
 		revs->limited = 1;
 		revs->prune = 1;
-		load_ref_decorations(NULL, DECORATE_SHORT_REFS);
 	} else if (!strcmp(arg, "--date-order")) {
 		revs->sort_order = REV_SORT_BY_COMMIT_DATE;
 		revs->topo_order = 1;

t/t4202-log.sh

@@ -837,7 +837,7 @@ test_expect_success 'decorate-refs and decorate-refs-exclude' '
 	test_cmp expect.decorate actual
 '
 
-test_expect_failure 'decorate-refs-exclude and simplify-by-decoration' '
+test_expect_success 'decorate-refs-exclude and simplify-by-decoration' '
 	cat >expect.decorate <<-\EOF &&
 	Merge-tag-reach (HEAD -> master)
 	reach (tag: reach, reach)