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>

builtin/merge.c

@@ -443,6 +443,7 @@ static void squash_message(struct commit *commit, struct commit_list *remotehead
 	}
 	write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 	strbuf_release(&out);
+	release_revisions(&rev);
 }
 
 static void finish(struct commit *head_commit,
@@ -998,6 +999,7 @@ static int evaluate_result(void)
 	 */
 	cnt += count_unmerged_entries();
 
+	release_revisions(&rev);
 	return cnt;
 }