bug#15286: Add the current directory as GUILE_LOAD_PATH by default

[Arne Babenhauserheide]

Dear Guix Hackers,

Currently to install a local package definition, I have to adjust the 
GUILE_LOAD_PATH by hand:

      GUILE_LOAD_PATH=. guix package -e '(@ (mercurial) hg)'

This could be much clearer if the $pwd were in the load path automatically.


Even clearer could be something like overlays as discussed on guix-devel.¹

Examples of usage could be:

# install from an explicit definition file
guix package --file mercurial.scm -i mercurial 

# install from a directory with many scheme files: essentially just
# adds the directory and subdirectories to the load path.
guix package --overlay . -i mercurial 

With the obvious short forms:
(--file | -f)
(--overlay | -o)

Overlay and file might be used multiple times to adjust the available
packages.


Adding the local path to the package would be a first step, but it
would be unnecessary if there were a way to define additional files
and overlays.


Best wishes,
Arne

¹: http://lists.gnu.org/archive/html/guix-devel/2013-08/msg00127.html