[PATCH] Automatically set `geiser-guile-load-path' from .dir-locals

[Maxim Cournoyer]

Hello Guix!

I've been experimenting with the following modification to the
.dir-locals file shipped with Guix, that allows setting per-buffer
variables within Emacs when visiting a file in the same directory (or in
one of its sub-directories).

This makes life a bit easier, by ensuring that a Geiser REPL started
with C-c C-a in a file of either the main 'guix' checkout, a
'guix-core-updates' worktree or a 'guix-staging' worktree will set up
the GUILE_LOAD_PATH and GUILE_LOAD_COMPILED_PATH correctly (via the
`geiser-guile-load-path' Elisp variable).

The only requirement for it to work reliably is that any Guix checkout
or worktree name should start with "guix".

It doesn't require Geiser to be installed (it will just set the above
variable uselessly if it isn't used -- not a big deal).

What do you think?  Is it useful?  Should we include this as part of the
default .dir-locals of Guix?

Patch to follow!

Thanks,

Maxim