I happily use vim as my default editor for commits, and do not wish to change it. However, when it comes to rebasing, I find myself squashing dozens and dozens of commits which
Try adding the GIT_EDITOR environment variable before your command, like so:
GIT_EDITOR
GIT_EDITOR= git rebase <...>
For example, to use nano I would type:
nano
GIT_EDITOR=nano git rebase -i abcdef1234