gh-138848: Add PNG optimization pre-commit hook

[StanFromIreland]

CC @zware The downside of adding the hook is we still have to deal with all of the little savings.

This currently uses the recommendations from their README.

• Issue: Add PNG optimization to pre-commit #138848

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📚 Documentation preview 📚: https://cpython-previews--138849.org.readthedocs.build/

[zware]

The downside of adding the hook is we still have to deal with all of the little savings.

IIUC, the pre-commit hook should only apply when the file is changed?

[StanFromIreland]

As you can see on this PR, running pre-commit [with --all-files as is done in our CI] will modify all existing files too, I don't know if there's a nice way to do it, other than listing every existing file.

[StanFromIreland]

As for git size:

$ git count-objects -v
count: 0
size: 0
in-pack: 1148637
packs: 1
size-pack: 339708
prune-packable: 0
garbage: 0
size-garbage: 0
$ git fetch upstream pull/138849/head:pr-138849
From https://github.com/python/cpython
 * [new ref]                 refs/pull/138849/head -> pr-138849
$ git count-objects -v
count: 0
size: 0
in-pack: 1148637
packs: 1
size-pack: 339708
prune-packable: 0
garbage: 0
size-garbage: 0

[hugovk]

I think you'll need exclude them:

• https://pre-commit.com/#config-exclude
• https://pre-commit.com/#regular-expressions

That way added files will be checked later.

[ned-deily]

FYI, the Using/mac-installer* files will be being updated shortly so please don't modify them now.

[StanFromIreland]

Oops, I messed up a merge.