Subject: Re: [RFC PATCH v2] shortlog: add group-by options for year and month

From: Jacob Stopak <[email-masked]>
Date: Fri, 23 Sep 2022 21:38:29 -0700

On Fri, Sep 23, 2022 at 05:58:56PM -0400, Jeff King wrote:
> I don't think you even really need the regexp. If we respect --date,
> then you should be able to ask for --date=format:%Y-%m.

Hmm I tried passing in --date=format:... to my patched shortlog command
along with setting some date placeholder like "... %cd ..." in the code,
but it's not picking up on the format. Do you know how the date format
can be wedged into the format_commit_message(...) "format" argument?

> Unfortunately there's no way to specify the format as part of the
> placeholder. The for-each-ref formatter understands this, like:
> 
>   %(authordate:format:%Y-%m)
>
> I wouldn't be opposed to teaching the git-log formatter something
> similar.

Oh that would solve my problem... Would it be a hefty effort to teach
this to the git-log formatter?

> But there's something else interesting going on in Jack's patch, which
> is that he's not just introducing the date-sorting, but also that it's
> used in conjunction with other sorting. So really the intended use is
> something like:
> 
>   git shortlog --group:author --group:%Y-%m

Yes I sort of stumbled on this and realized that this way I wouldn't have
to touch the actual sorting or grouping functionality at all, which was
already working properly. I just needed to reformat the shortlog message to
include the year and/or month in a way that kept things consistent.

> I think we'd want to allow the general form to be a series of groupings.
> In the output from his patch it looks like:
> 
>   2022-09 Jeff King
>      some commit message
>      another commit message
> 
> I.e., the groups are collapsed into a single string, and unique strings
> become their own groups (and are sorted in the usual way).
> 
> If you give up the regex thing, then that naturally falls out as
> (imagining we learn about authordate as a placeholder):
> 
>   git shortlog --group='%(authordate:format=%Y-%n) %an'
> 
> without having to implement multiple groupings as a specific feature
> (which is both more code, but also has user-facing confusion about when
> --group overrides versus appends). That also skips the question of which
> --group-by-regex applies to which --group-by-value.
> 
> I do agree the regex thing is more flexible, but if we can't come up
> with a case more compelling than subsystem matching, I'd just as soon
> add %(subject:subsystem) or similar. :)
> 
> -Peff

I like this idea too. Since it requires a larger re-implementation,
maybe I can pursue this going forward. I assume if we did this we would
keep the existing group options like "--group=author" as shortcuts, and
refactor them behind the scenes to use the new method. If so it may be
useful to add my originally suggested options of "--group=year" and
"--group=month" as well for convenient default time-based groupings.

How do you feel about me submitting a v3 patch of my initial suggested
implementation of new group options for year and month? Then going forward
I can work on generalizing the grouping feature the way Peff suggested.

-Jack