revisions API users: add straightforward release_revisions()

Add a release_revisions() to various users of "struct rev_list" in
those straightforward cases where we only need to add the
release_revisions() call to the end of a block, and don't need to
e.g. refactor anything to use a "goto cleanup" pattern.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

midx.c

@@ -1061,6 +1061,7 @@ static struct commit **find_commits_for_midx_bitmap(uint32_t *indexed_commits_nr
 	if (indexed_commits_nr_p)
 		*indexed_commits_nr_p = cb.commits_nr;
 
+	release_revisions(&revs);
 	return cb.commits;
 }