Skipping the buffer extension .~HEAD~ when choosing major mode during ediff session

[Nordlöw <per.nordlow@gmail.com>]

Is there a simple way for emacs to ignore the .~HEAD~ suffix when its
chooses its major-mode based on name of the file/buffer. The .~HEAD~
suffix is typically appended to a temporary buffer name created when
we ediff a file with its vc head version.

The brute-force and ugly way is of course to modify all entries in
auto-mode-alist but that seems far too cumbersome.

If nobody has any clue should I start digging into the code where auto-
mode-alist is used?

Thanks in advance,
Nordlöw