chore(internal/actions): refactor changefinder

[noahdietz]

Refactors changefinder to support nested submodules i.e. vision/v2.

Changes the default compare the current HEAD against origin/main.

Add a -q quiet mode, all logs will be buffered and dumped in the event of an error.

Add a -dir flag to specify a different root dir than the default of cwd.

Add a -format flag with values plain (stdout, new line delimited), and github (prints github action output). Defaults to plain.

Add a -gh-var flag that accepts the name of the GitHub variable the output should set, defaults to submodules.

This will be able to replace the git-fu used in the apidiff workflow and it can power a "change description" action, basically the inverse of the apidiff workflow that reports the added surfaces.

Try it out by running the following:

cd $GOOGLE_CLOUD_GO
git checkout origin owl-bot-copy
go run ./internal/actions/cmd/changefinder -q

[quartzmo]

I wasn't aware of changefinder before this PR. It doesn't appear to have any documentation whatsoever. What do you think about adding a short README or even just a few sentences of function docs for main? The description for this PR has some useful content.

[noahdietz]

I wasn't aware of changefinder before this PR. It doesn't appear to have any documentation whatsoever. What do you think about adding a short README or even just a few sentences of function docs for main? The description for this PR has some useful content.

Great idea.

Honestly, I wasn't aware of it either until I started to consider writing the exact same thing and bumped into it while starting to do so :)

[quartzmo]

I think this module and file are currently orphaned. It was added in #4537 and referenced only in .github/workflows/release-submodule.yaml, which no longer exists.

[noahdietz]

I think this module and file are currently orphaned. It was added in #4537 and referenced only in .github/workflows/release-submodule.yaml, which no longer exists.

Well I'm glad it wasn't removed, because it's quite useful!

[quartzmo]

Can you add your new usage(s) to this PR?

[noahdietz]

Can you add your new usage(s) to this PR?

If it is OK, I'd prefer to make that change in a separate PR in case I need to revert it (i.e. i break the apidiff workflow).

[noahdietz]

Add a README!