use strbuf_addstr() for adding strings to strbufs

Use strbuf_addstr() instead of strbuf_addf() for adding strings.  That's
simpler and makes the intent clearer.

Patch generated by Coccinelle and contrib/coccinelle/strbuf.cocci;
adjusted indentation in refs/packed-backend.c manually.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/branch.c b/builtin/branch.c
index 355f9ef..a2b7c55 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -352,7 +352,7 @@ static char *build_format(struct ref_filter *filter, int maxwidth, const char *r
 			strbuf_addf(&obname, "%%(objectname:short=%d)", filter->abbrev);
 
 		strbuf_addf(&local, "%%(align:%d,left)%%(refname:lstrip=2)%%(end)", maxwidth);
-		strbuf_addf(&local, "%s", branch_get_color(BRANCH_COLOR_RESET));
+		strbuf_addstr(&local, branch_get_color(BRANCH_COLOR_RESET));
 		strbuf_addf(&local, " %s ", obname.buf);
 
 		if (filter->verbose > 1)