Easier ability to combine stacks

[ice1080]

I ran into a need to move one stack to be on top of another stack. It took me several tries to get this right, and the final commands required fully unstacking both stacks in the remote and then re-stacking every branch for both stacks, and the final rebase/push/submit.
Adding the ability to change the trunk branch of a stack to any other branch would be great. Ideally it would recognize when the new trunk is already in another stack, and update both stacks accordingly.

[anilanar]

In Graphite, this is called gt move, allows rebasing stacks on top of other stacks or on top of another trunk. This is a must feature for us.

[bhamiltoncx]

+1; I'm really surprised this isn't a core feature of gh-stack.