I like auto-fill-mode and even have it customized for LaTeX-mode in my Emacs configuration. However, while working with other people via a distributed version control system, like I do with my friends, auto-fill-mode can be a real pain if not everyone uses it. Whenever the ones that do commit any code, others are annoyed because it’s difficult to see the changes in the diff file, since auto-fill-mode reformats paragraphs (hence producing ‘more’ changes).

The most straightforward solution is to put some local variables into the file, like (auto-fill-mode -1), but today at StackOverflow I saw a much neater solution: one can put a function that searches for a specific string inside a file and sets minor-modes accordingly. So now there’s a coauthors search function in my .emacs:

; auto-fill is enabled for TeX...
(add-hook 'LaTeX-mode-hook 'turn-on-auto-fill)
; ...unless I work with the gang
(defun my-auto-fill-disabling-hook ()
  "Check to see if we should disable autofill."
  (save-excursion
    (when (or (re-search-forward "truls" 1000 t)
              (re-search-forward "sjur" 1000 t)
              (re-search-forward "erik" 1000 t))
      (auto-fill-mode -1))))
(add-hook 'find-file-hooks 'my-auto-fill-disabling-hook)