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>

bisect.c

@@ -884,6 +884,7 @@ static int check_ancestors(struct repository *r, int rev_nr,
 	/* Clean up objects used, as they will be reused. */
 	clear_commit_marks_many(rev_nr, rev, ALL_REV_FLAGS);
 
+	release_revisions(&revs);
 	return res;
 }
 
@@ -964,6 +965,7 @@ static void show_diff_tree(struct repository *r,
 
 	setup_revisions(ARRAY_SIZE(argv) - 1, argv, &opt, NULL);
 	log_tree_commit(&opt, commit);
+	release_revisions(&opt);
 }
 
 /*