Allow auto deployment of test versions to App Engine

[tunetheweb]

It can be handy to build a test deployment for a branch as easier to review the pull request once you see something in action. We've used this a few times and it's quite handy - especially for those without the full dev environment set up or less technical in nature.

This will be especially useful as chapters start to be submitted by authors now.

Thoughts:

• Auto-deploy on opening a pull request with .*py, *.json, .*md, .*html, *.js or .css (i.e. basically everything but PRs with only *.sql files). Or maybe just on every PR open if easier?
• Only deploy on completion of successful build.
• Ability to redeploy somehow (e.g. if a certain comment (GitHub deploy) or label is added?) as I think redeploying on every push to an open pull request could be too much.
• Run through GitHub actions.
• The action should comment on the PR with the test deploy URL.
• Also add ability to manually deploy for a branch
• What about auto deploying a test version on merge to master as well?
• Should have some clear down job of test deployments - either when PR is accepted, or nightly/weekly.
• Need to keep our App Engine account secure but tested using GitHub secrets and believe it can be made secure (will test some more).

We've got a service account set up so will start testing this but opening this issue to track this and invite comments/suggestions.

If this goes well, perhaps could consider deploying to prod as well through manual triggering of a separate action? Will open a separate issue for that once this one is resolved as it has other things to consider e.g. version numbering, how to update release (I've an open issue with GitHub CLI that would be needed to fully automate this)) and when to auto deploy. But noting here as long term goal.

[rviscomi]

Auto-deploy on opening a pull request with .*py, *.json, .*md, .*html, *.js or .css (i.e. basically everything but PRs with only *.sql files). Or maybe just on every PR open if easier?

A different heuristic that could be useful may be "did any of the prod files change as a result of building the PR?" For sql the answer would be no, so nothing to deploy/stage.

[tunetheweb]

As discussed on slack, closing this until Github gives us better ways to restrict access to secrets to certain branches or users.