My problem stems from Emacs inserting the coding system headers into source files containing non-ascii characters:
# -*- coding: utf-8 -*-
My coworkers do not like these headers being checked into our repositories. I don't want them inserted into my files because Emacs automatically detects that the file should be UTF-8 regardless so there doesn't seem to be any benefit to anyone.
I would like to simply set Emacs to use UTF-8 automatically for all files, yet it seems to disagree with this idea. In an effort to fix this, I've added the following to my .emacs:
(prefer-coding-system 'utf-8)
(setq coding-system-for-read 'utf-8)
(setq coding-system-for-write 'utf-8)
This does not seem to solve my problem. Emacs still inserts the coding-system headers into my files. Anyone have any ideas?
EDIT:
I think this problem is specifically related to ruby-mode. I still can't turn it off though.
By default, Emacs will not write file variables into your files. You must have asked it to do so somewhere in your .emacs. Try running emacs -q and see if the file variables get inserted.