Re: Multiple versions

[Pjotr Prins]

On Sun, Dec 27, 2015 at 12:20:27PM +0300, Dmitry Bogatov wrote:
> Currently, I am at master branch. I want install parallel-20151122.
> But it is gone since 0877e. I propose to keep *all* versions,
> but just 'parallel' refer to latest.

Use a combination of git hash values (to generate the versions) and
guix profiles (to manage them at the same time).

> In case of haskell/python/ruby libraries, I propose keep all versions
> multiplied by every version of compiler/interpreter.

I do the same with Ruby using profiles. I have any number of interpreters
installed for testing and any number of libraries using either guix or
the lib path with a profile in there.

It can all be done, but it is not the job of guix to to manage beyond
profiles. I do think we should have transparent git HASH tagged
installs, e.g., 

guix package -i ruby --git-hash HASH

which would checkout a git tree and run something like ./pre-inst-env
under the hood.  What we do by hand now can be done automatically. But
that is a wider subject.

With regard to your emacs question, better post it with a separate
subject title. It got lost now.

Pj.