Re: master daea9b3 1/2: Read mailcaps again only when necessary

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: monnier@iro.umontreal.ca,  gregory@heytings.org,  emacs-devel@gnu.org
> Date: Mon, 01 Nov 2021 18:29:12 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > What if we have the same file name in several different directories --
> > how will you record the files so they all get different hash slots?
> 
> Oh, you mean relative file names?  I think it's up to the caller to
> decide.  If they don't want that, then give an absolute file name, and
> if they do want that, then don't.

But that's contrary to every other Emacs function that accepts file
names.  They all interpret the file names relative to the
default-directory.  And so do the primitives the current
implementation of file-has-changed-p: they expand the file name
internally.  But the file name that gets recorded in the hash table
does not follow that rule, and that is the problem.  because this way
it makes no sense to use relative file names, unless the caller asks
for trouble.  So in practice, every caller will have to pass an
absolute file name, which again is different from all the other APIs
we have that accept file names.

Once again, the key for recording the time stamp is the file name you
pass, so that key must be unique, and that means file-truename.