[PATCH 0/7] shortlog: introduce `--group=<format>`

This series is based on a suggestion[1] from Junio in response to Jacob Stopak's series to add committer month/year options as shortlog groups.

This series pursues a more flexible approach, where arbitrary pretty formats can be used to generate group names in shortlog. For example, to group by committer month/year, you can do the following:

    $ git.compile shortlog -s --group='%cd' --date='format:%Y-%m' v2.37.0..
       117  2022-06
       274  2022-07
       325  2022-08
       271  2022-09
        17  2022-10

, which is cute. It can also be used to reimplement existing functionality in shortlog, which is what the final three patches in this series do. Author and committer options are implemented under the hood as if they were shorthands for `--group='%aN <%aE>'` (or `--group='%cN <%cE>'`, respectively).

The `--group=trailer:<key>` option is also reimplemented, but it is slightly trickier than the rest. See the final patch for more details there.

Thanks in advance for your review.

[1]: https://lore.kernel.org/git/xmqqillevzeh.fsf@gitster.g/

Jeff King (1):
  shortlog: accept `--date`-related options

Taylor Blau (6):
  Documentation: extract date-options.txt
  shortlog: extract `--group` fragment for translation
  shortlog: support arbitrary commit format `--group`s
  shortlog: implement `--group=author` in terms of `--group=<format>`
  shortlog: implement `--group=committer` in terms of `--group=<format>`
  shortlog: implement `--group=trailer` in terms of `--group=<format>`

 Documentation/date-options.txt     |  66 +++++++++++++
 Documentation/git-shortlog.txt     |   4 +
 Documentation/rev-list-options.txt |  67 +------------
 builtin/log.c                      |   1 +
 builtin/shortlog.c                 | 145 +++++++++++++++--------------
 shortlog.h                         |   6 +-
 t/t4201-shortlog.sh                |   9 ++
 7 files changed, 163 insertions(+), 135 deletions(-)
 create mode 100644 Documentation/date-options.txt