Re: Add the git commit id to the generation information

[Roel Janssen <roel@gnu.org>]

Ricardo Wurmus writes:

> Hi Roel,
>
>> I have a feature request.
>>
>> When I run 'guix pull', install a package, run 'guix pull' again (on
>> another day), and install another package, I'd get two generations:
>>
>>> Generation 181  May 22 2017 11:47:37
>>>  + haunt        0.2.1   out     /gnu/store/x2bkpzrdbaxavl29r2xg0fip1jjici9q-haunt-0.2.1
>>>
>>> Generation 182  May 24 2017 09:52:06    (current)
>>>  + guile-commonmark     0.1     out     /gnu/store/k8vq65czfb8k4hvvjvsca34scd9xsxik-guile-commonmark-0.1
>>
>> Now, if I'd like to go to the Guix packages source code of generation
>> 181, I can only guess at which actual state of the Guix repository this
>> was, because this timestamp is the timestamp of creating the generation,
>> not the timestamp of the Guix package state.  So, I'd like to propose to
>> add the commit id to the generation like so:
>>
>>> Generation 181  May 22 2017 11:47:37    (ae548434337cddf9677a4cd52b9370810b2cc9b6)
>>>  + haunt        0.2.1   out     /gnu/store/x2bkpzrdbaxavl29r2xg0fip1jjici9q-haunt-0.2.1
>>>
>>> Generation 182  May 24 2017 09:52:06    (current)
>>>  + guile-commonmark     0.1     out     /gnu/store/k8vq65czfb8k4hvvjvsca34scd9xsxik-guile-commonmark-0.1
>
> What would be the expected behaviour in the presence of
> GUIX_PACKAGE_PATH?  I could have had GUIX_PACKAGE_PATH set pointing to a
> module containing a custom variant of haunt.
>
> I do agree that it would be very useful to know more about the state of
> Guix for any given generation.  However, that state is more complex than
> a single commit.

Oh, indeed..  Any suggestions?

My other thought on this, is to add a tagging mechanism, that users can
simply add tags to a generation, of which one could be the commit id.

I think that having the upstream git commit ID already improves the
situation.  Adding external repositories is not something the upstream
distribution can take care of.  Maybe if we would add a different, more
formal way of allowing external repositories, that could be dealt with
more easily.  (Is this what 'channels' could do?)

Kind regards,
Roel Janssen