Fixed issue #2135: Add menu button to open Explorer when clone finishes

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Disallow combine commit if selected commits above HEAD

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Prevent to add files to list more than once

All added files have been listed, it done there.
Don't go next iteration in that loop.

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>