(This might be a little niche...)

It might make sense to allow different EDITOR selection for "edit file" action then for "edit commit message" action.
My reasoning here is that "edit commit" (and probably all of git actions that require editor) is a blocking action - git waits for the editing to complete before continuing. "Edit a file", OTOH, might be a long operation - open the file in my IDE in a separate window, and continue whatever it was I was doing in tig in this terminal - like maybe open a couple more files from the same diff.

(In my case, I use Notepad++ for "long edits" and Nano for "short" ones, because it's hard to setup N++ to "blocking" mode).