Extending Guix without using the Guile load path

[Ricardo Wurmus]

Hi Guix,

I think it’s a bit difficult to install the Guix Workflow Language at
this point and I’d like to change that.

Currently, new sub-commands for Guix are looked up by module name on the
Guile load path.  When installing the “gwl” package, though, the Guile
load path is not automatically altered, so users need to set it up by
themselves.  The load path is only altered automatically when users
install the “guile” package.  This is not a good recommendation because
users may have Guile 2.2 in their profile, and not Guile 3.0 or whatever
version may be needed by the extension.

I wonder if we can make this a little nicer by letting Guix look for
sub-command scripts in directories that are listed in an environment
variable, such as GUIX_EXTENSIONS_PATH.  The “guix” package would set
this search path and packages wanting to provide a sub-command (such as
“guix workflow” or “guix home”) would arrange to have their scripts
placed in that sub-directory of their outputs.

What do you think?

--
Ricardo