bug#27933: emacs25: default info dir initialization slow with remote filesystems

[Lars Ingebrigtsen]

Glenn Morris <rgm@gnu.org> writes:

> Ideally Info-default-directory-list would go away. leaving only
> Info-directory-list initialized in a standard fashion. But I haven't
> looked at the details.

I poked a bit at this, and it seems hard to make this work in a
backwards-compatible way.  The problem is that we document stuff like
this to work:

(add-to-list 'Info-default-directory-list "~/Info")

And we compute Info-default-directory-list at startup (and it stats a
bunch of directories, which is what this bug report is about).  The user
can therefore assume that it's been filled, and may be removing
directories from it, too, so if we just initialise it (or do statting
while initialising Info-directory-list), we'll be breaking people's
setups.  I.e., people may have

(setq Info-default-directory-list (delete "/usr/share/info/" 
Info-default-directory-list))

in .emacs, and that won't work.

But I think we should indeed fix this, because statting those
directories at startup isn't ideal, but it'd be a breaking change.

I propose to make Info-default-directory-list nil by default, and
initialise Info-directory-alist from the directories that
Info-default-directory-list would normally find, as well as
Info-default-directory-list (unless INFODIR is set, and that overrides).

I think the breakage for users should be pretty minimal -- it would only
affect people that remove stuff from Info-default-directory-list, but
not those that add to it.

Any comments before I make this change?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no