Atom on Mac: Close window to terminate process

I use Atom as my git commit/rebase message editor. And I'm on Mac. I know that atom -w can be used to keep git waiting until the Atom process is terminated. However, my problem is, often time, I have some other Atom windows already open for other documents. When git commit, the new Atom window starts. I edit my commit message, close the window. On Mac, closing a window will not trigger process termination. So git will still be waiting. I have two choices here:

1. Terminate all Atom processes by pressing Command+Q. This way I will have to save all unsaved change in other windows.
2. Use ps or top to find the atom -w process ID and kill it. Obviously this is not user friendly.

Am I missing something here? Can I tell Mac that when all foreground windows of this process are closed, terminate the process like Windows? Or can Atom do something that terminates its process when I close its window or last tab?