Re: Emacs local variables sections in files; time-stamping

[Glenn Morris]

Eric Blake wrote (on Tue, 22 Feb 2011 at 16:38 -0700):

> > Firstly, a minor point. write-file-hooks is obsolete since Emacs 22.1,
> > replaced by write-file-functions. (Actually, the Emacs documentation
> > suggests using before-save-hook for time-stamping.)
> 
> And what's the portable fallback, for files that might be maintained on
> older emacs?

If you want to be compatible with Emacs older than 22.1, stick with
write-file-hooks (it might go away in some distant future Emacs).
Otherwise you can use before-save-hook.

> Do you have a suggestion for an alternate way to ensure that the
> timestamps are consistently updated when edited in their primary
> upstream repo, without the use of the eval?  For example, would creating
> a .dir-locals.el in the same repository do the trick?  And, showing how
> little I know about .dir-locals.el, what would its contents have to be
> to take the place of the eval?

Wow, you require everyone with commit rights to use Emacs? ;)

Actually, I discovered that Emacs has a feature for this (of course)!

`safe-local-eval-forms' contains eval: things that are actually safe.
By default, it includes:

  (add-hook 'write-file-functions 'time-stamp)
  (add-hook 'before-save-hook 'time-stamp)

So if you change to using 'before-save-hook, there will no longer be a
confirmation prompt. Or I guess we should add:

  (add-hook 'write-file-hooks 'time-stamp)

to the default list as long as write-file-hooks is still supported in
Emacs.


With regards to dir-locals, I think you can do it using a file containing:

  ((nil . ((eval . (add-hook 'before-save-hook 'time-stamp)))))

This requires Emacs >= 23.1. For some reason, Emacs < 23.2 will warn
about that evalling that form.