add init-pants action input.experimental-remote-cache-via-gha

[cognifloyd]

This makes the documented workflow step available via a simple boolean input flag:
https://www.pantsbuild.org/2.20/docs/using-pants/remote-caching-and-execution/remote-caching#workflow

Also, I noticed the README was out of date, so I updated it.

[benjyw]

noice!

Worth a quick blog post?

[cognifloyd]

A blog post would be great. I don't have enough bandwidth to work on that though. This is a drive-by PR trying to simplify experimenting with this in the StackStorm repo.

Hopefully someone who is more versed in the new feature can write a blog post.

[huonw]

Nice one! Thanks @cognifloyd . Looking at this, I wonder if the recipe (and this action) could also set PANTS_REMOTE_PROVIDER=experimental-github-actions-cache to make this truly "one button"... but maybe we should only do that once it's non-experimental.

Worth a quick blog post?

I'm a bit nervous about a blog post due to pantsbuild/pants#20133 / actions/cache#1280 : we'll be publicising something we know doesn't work. But, maybe trying to get publicity about that would help GH prioritise work on it higher.

[cognifloyd]

Nice one! Thanks @cognifloyd . Looking at this, I wonder if the recipe (and this action) could also set PANTS_REMOTE_PROVIDER=experimental-github-actions-cache to make this truly "one button"... but maybe we should only do that once it's non-experimental.

I thought about trying to set the other options via env vars, but I'm not sure if all options can be set by env var, or just those that opt in like the password for twine. So, I opted to just follow the documentation and make sure people are thinking about the downsides before fully enabling this.

I like the idea of making it "one button" once it comes out of experimental.

[cognifloyd]

I'm a bit nervous about a blog post due to pantsbuild/pants#20133 / actions/cache#1280 : we'll be publicising something we know doesn't work. But, maybe trying to get publicity about that would help provide GH prioritise work on it higher.

Yes. In my experimentation, I hit the rate limit really quickly even though I'm not using pants for very much yet. If we publish a blog post, it should include a section detailing the short comings and a plea to GitHub to improve the situation.