tag.c: use the correct algorithm for the '--contains' option

In b7cc53e (tag.c: use 'ref-filter' APIs, 2015-09-11) we port tag.c
to use the ref-filter APIs for filtering and printing refs.  In
ref-filter we have two implementations for filtering refs when the
'--contains' option is used.

Although they do the same thing, one is optimized for filtering
branches and the other for tags (borrowed from branch.c and tag.c
respectively) and the 'filter->with_commit_tag_algo' bit decides
which algorithm must be used.  We should unify these.

When we ported tag.c to use ref-filter APIs we missed out on setting
the 'filter->with_commit_tag_algo' bit.  As reported by Jerry
Snitselaar, this causes "git tag --contains" to work way slower than
expected, fix this by setting 'filter->with_commit_tag_algo' in
tag.c before calling 'filter_refs()'.

Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Tested-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/tag.c

@@ -52,6 +52,7 @@ static int list_tags(struct ref_filter *filter, struct ref_sorting *sorting, con
 	}
 
 	verify_ref_format(format);
+	filter->with_commit_tag_algo = 1;
 	filter_refs(&array, filter, FILTER_REFS_TAGS);
 	ref_array_sort(sorting, &array);