tools: add a script to auto merge remote and local branches

this script was written by me in about 3 minutes, please
keep in mind is still really experimental haha.

eg it doesnt detect merge conflicts and just carries on.
it also doesnt detect if there are new changes etc.
it simply carries out its stupid task.

but yeah, no risk, no fun.

Change-Id: I5e95abaeb9e8baa2390ae89a70a99bab38827e0b