Hi,

zimoun <zimon.toutoune@gmail.com> skribis:

> Let’s describe the use case.  Consider that:
>
>   guix time-machine -C channels -- install foo
>
> is provided in some documentation, say scientific paper.  Where the
> channels.scm file is completly described:
>
> (list (channel
>         (name 'kikoo)
>         (url "https://example.org/that-great.git")
>         (commit
>           "353bdae32f72b720c7ddd706576ccc40e2b43f95")))
>
> In the future, if https://example.org/that-great.git disappears, then
> build/install the package ’foo’ is becoming difficult, nor impossible.
>
> However, let’s consider that the repo ’that-great’ had been saved in SWH
> (say manually); since it is a regular Git repo.  Guix should be able to
> fallback to it transparently.

I went head-down to add SWH fallback to ‘latest-repository-commit’… but
that’s of no use because (guix channels) wants a complete clone so that
it can determine commit relations (to detect downgrades).

The SWH vault gives access to checkouts primarily, but it’s also
possible to get a full repo in ‘git fast-import’ format, which is what
we need:

  https://archive.softwareheritage.org/api/1/vault/revision/gitfast/doc/

However, this API will be eventually replaced by some other solution say
SWH developers, possibly a bare Git repo export, so it may not be a good
idea to build upon it.

If we were able, using the SWH API, to map “revisions” to “origins”, we
could find potential mirrors hosting a given commit, but apparently
that’s not possible.

To be continued…

Ludo’.