Package transformations

[Ludovic Courtès]

Hello!

I’ve pushed my “train hacks”, which are a continuation of refactoring
work I had done in December (ca. 64ec0e2):

  • ‘guix build’ has a new ‘--with-input’ option to rewrite the
    dependency graph so you can run:

      guix build guix --with-input=guile=guile-next

    and guess what it does.  :-)

    However, it only works for explicit inputs.

  • ‘guix package’ supports ‘--with-source’ and ‘--with-input’, with the
    caveat that such transformations are forgotten upon upgrades.

  • There’s a fairly generic package transformation framework in (guix
    scripts build).

  • The documentation of command-line build options is a bit improved,
    with subsections for each category of options.

Feedback welcome!

Ludo’.