bug#51523: 29.0.50; gnus-mime-view-part-externally very slow

[Gregory Heytings]

> > I attach an improved version of file-has-changed-p.  Following Eli's 
> > suggestion, it records the file size together with its timestamp.
>
> What about expand-file-name or file-truename?  That problem still exists 
> in this new patch, AFAICT.

I don't know what I should do here.  Both Stefan and Lars think (IIUC) 
that it's okay to use the filename as is.  I tend to agree with them; 
after all, the filename is only used as a key in the hash table, and 
file-attributes finds the "right" file anyway.

Using expand-file-name or file-truename also makes that function much 
slower: (benchmark-run 100000 (file-has-changed-p "~/.profile")) takes (on 
my computer) 2 seconds in its current version, 3 seconds with 
expand-file-name, and... 10 seconds with file-truename.