On Thu, Jun 30 2022, Siddharth Asthana wrote:

git cat-file is not a plumbing command anymore, especially as it gained
more and more high level features like its `--batch-command` mode. So
tools do use it to get commit and tag contents that are then displayed
to users. This content which has author, committer or tagger
information, could benefit from passing through the mailmap mechanism,
before being sent or displayed.

This patch adds --[no-]use-mailmap command line option to the git
cat-file command. It also adds --[no-]mailmap option as an alias to
--[no-]use-mailmap.

I think I know the answer, but I think it would be helpful to discuss
the underlying motivations too. I.e. an obvious alternative is "why not
just get this information out of git show/log then?".

The "I think I know the answer" being that I suspect this is to cater to
gitaly having persistent "cat-file" processes around, whereas for "git
log" it would entail spinning up a new process per-request.

But maybe I'm missing something :)

So not as a blocker for this change, which I think can be made small
enough to be justified in cat-file, but just for context: If "git log"
had a similar --batch mode, would there be a need for this change, or is
this just adding a common case to "cat-file" to "tide us over" (as it
were) while that sort of thing doesn't exist yet (and maybe never will
:()?