Re: Data Services: use cases

[Christopher Baines <mail@cbaines.net>]

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

> Cool!  I have seen that you added the commit!  Great.
>
> On Mon, 16 Nov 2020 at 20:54, Christopher Baines <mail@cbaines.net> wrote:
>
>>>>> 2: <https://lists.gnu.org/archive/html/guix-devel/2020-10/msg00096.html>
>
>>>> The Guix Data Service stores the date in the email from the Git hook
>>>> that runs when one pushes to Savannah. That's the date you see for a
>>>> revision, and it should be pretty close to when it actually showed up in
>>>> the Git repository. It's not perfectly accurate, but it should be better
>>>> than either the commit date or author date from the Git metadata.
>
>>> Maybe my investigations in [2] above are wrong but which date from the
>>> email the Data Service is using?
>
> I do not know what is wrong, but some thing is.  From
>
>   https://lists.gnu.org/archive/html/guix-devel/2020-10/msg00096.html
>
> the commit ranges:
>
> https://data.guix.gnu.org/repository/1/branch/master/package/ghc-haddock/output-history
>
> does not match with the Git history if I am not wrong.
>
> The first commit producing j5llsz…-ghc-haddock is not
> 3922208091 but 12dc9f58c4.  And then compare:
>
>                 author date              commit date
> 3922208091|Thu Jul 23 14:03:19 2020|Fri Jul 24 14:21:31 2020
> 12dc9f58c4|Fri Jul 24 09:56:25 2020|Fri Jul 24 14:21:30 2020
>
> I have not checked what guix-commits says.  Maybe the mess is
> overthere.

The author date and commit date won't necessarily match the date
whatever branch is updated (and it's when that branch was updated that
the Guix Data Service tries to store).

Generally, the author date will match or precede the commit date, which
will match or precede the date the commit hit whatever branch.

Taking 3922208091 as an example, I pulled the commit dates in UTC [1]:

AuthorDate:        Thu Jul 23 12:03:19 2020
CommitDate:        Fri Jul 24 12:21:31 2020
Guix Data Service: 2020-07-24 12:22:11 [2]


1: TZ=UTC git show --pretty=fuller 3922208091
2: https://data.guix.gnu.org/revision/39222080911eaf3d7f74effe4467c1a04464aef3

I think the author date says something about when the commit was
originally created. Rebasing and adding the Signed-off-by by bit will
update the commit date (but not the author date). Finally, the Guix Data
Service will store when the branch was updated (it uses the date of the
email as a proxy for this).

Does that clear things up?

Chris

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