Revert "sequencer: remove useless get_dir() function"

This reverts commit 39784cd362.

The function had only one caller when the "remove useless" was
written, but another topic will soon make heavy use of it and more
importantly the function will return different paths depending on
the value in opts.

sequencer.c

@@ -47,6 +47,11 @@ static inline int is_rebase_i(const struct replay_opts *opts)
 	return 0;
 }
 
+static const char *get_dir(const struct replay_opts *opts)
+{
+	return git_path_seq_dir();
+}
+
 static const char *get_todo_path(const struct replay_opts *opts)
 {
 	return git_path_todo_file();
@@ -155,7 +160,7 @@ int sequencer_remove_state(struct replay_opts *opts)
 		free(opts->xopts[i]);
 	free(opts->xopts);
 
-	strbuf_addf(&dir, "%s", git_path_seq_dir());
+	strbuf_addf(&dir, "%s", get_dir(opts));
 	remove_dir_recursively(&dir, 0);
 	strbuf_release(&dir);