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

> As discussed today at our weekly meeting, it could be cool to add the
> option:
>
>   guix git log --date=YYYY-MM-DD
>
> listing the first (resp. last) commit date of the day.  Or maybe all the
> commits of the days.  Using this information would be really useful to
> feed “guix time-machine”.  The use case I am interested is to easily
> find the commit when I only know the date of publication/submission of
> the paper.

I'd be a little careful about the implementation of this, commits have a
commit date, and author date, but neither of these things tell you when
commits were on a given branch.

Take the following commit for example:
f5f642058a3b6bf3eda5eb714ad5fa1f0a2b1b20 [1]

Would it be shown when running the following?

  guix git log --date=2021-01-17

It's commit date is the 17th, so maybe yes? But this commit didn't
actually turn up on the master branch until the 18th, at least according
to the Guix Data Service [2].

Taking your paper use case, if I produce some results on the 17th, even
perhaps stating the time down to the second, and then you using the
commit date of commits try to reproduce the environment, you're going to
get some commits that I didn't have.

Approaches that work most of the time, or have subtleties that might not
be immediately obvious make me a little nervous.

1:
commit f5f642058a3b6bf3eda5eb714ad5fa1f0a2b1b20
AuthorDate: Sun Jan 3 16:26:16 2021
CommitDate: Sun Jan 17 23:07:29 2021

    gnu: wxmaxima: Update to 20.12.2.

2: https://data.guix.gnu.org/revision/f5f642058a3b6bf3eda5eb714ad5fa1f0a2b1b20