Re: Preparing for an alpha release

[ludo@gnu.org (Ludovic Courtès)]

Hello,

Nikita Karetnikov <nikita.karetnikov@gmail.com> skribis:

>> things related to command-line tools, such as options documented and
>> not implemented in ‘guix-package’;
>
> I'd like to implement '--roll-back' and '--search'.

Cool!

> Questions:
>
> scheme@(guile-user)> ,use (guix-package)
> scheme@(guile-user)> %current-profile
> $1 = "/nix/var/nix/profiles/per-user/root/guix-profile"
> scheme@(guile-user)> %profile-directory
> $2 = "/nix/var/nix/profiles/per-user/root"
> scheme@(guile-user)> %user-environment-directory
> $3 = "/root/.guix-profile"
>
> 'ls' doesn't list the above. Why?

$1 gets created only once you’ve run ‘guix-package --install’.

And $3 has to be created manually, currently.  Probably ‘guix-package’
should create it automatically.  It’s just a fixed symlink to $1.

> How should '--roll-back' work?

Just change /nix/var/nix/profiles/per-user/root/guix-profile to point to
/nix/var/nix/profiles/per-user/root/guix-PREV-profile, where PREV is the
previous generation number (see ‘latest-profile-number’ in guix-package.)

> Does Guix support multiple profiles?

Yes: see the --profile option of guix-package.  Same as for nix-env.

> Nix uses the following scheme. [1]
>
> # ls /nix/var/nix/profiles/
> default          default-2-link  default-5-link  default-8-link
> default-10-link  default-3-link  default-6-link  default-9-link
> default-1-link   default-4-link  default-7-link  per-user
>
> What function should be used to access the pointee of 'guix-profile'?

You could use (readlink %current-profile), and then the %PROFILE-RX
regexp of ‘latest-profile-number’ to extract the profile number.

> I assume that it should work like this:
>
> 1. Get the pointee of 'guix-profile'.
>
> 2. Parse the name of the pointee.
>
> 3. Decrement the number and save that as '%current-profile'.

Yes, that’s the idea.  And then (delete-file %current-profile) and
(symlink new-profile %current-profile).

> Should 'guix-package' also support '--switch-generation',

Likewise: delete %current-profile and make it point elsewhere.

> '--list-generations',

List the files in %PROFILE-DIRECTORY matching %PROFILE-RX.

> and '--switch-profile'? [1]

Not sure about this one, but it’s basically changing a symlink’s target
again.

> How to implement '--search'?

User would provide a regexp, and you would use ‘fold-packages’ to
traverse all the packages and pattern-match each synopsis and
description, and return the matching packages.

How does that sound?

Thanks!

Ludo’.