bug#28408: 26.0.50; support git rebase in vc-dir

[Tom Tromey]

Lars> Doesn't the normal vc flow take care of that without the user having to
Lars> know about anything?  Admittedly, I seldom see any conflicts while
Lars> rebasing, so I may be misremembering, but I think Emacs just lets you
Lars> fix the merge errors, commit, and then everything's fine?

"rebase -i" is a mode that lets you reorder commits, squash commits, or
stop in the middle and edit or add new commits mid-rebase... it's not
really about conflicts or pull.  It's the typical git thing where the
same command may mean wildly different things depending on the
arguments.

Tom