brew pr-pull: handle label for merging without bottles

[nandahkrishna]

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This PR adds a --no-bottle option to pr-pull and pr-publish. This can be convenient when we want to rebase and merge a PR (and ensure commits are signed) without downloading bottles.

A use case for this would include PRs such as Homebrew/homebrew-core#80302 where we didn't add the syntax only label, since some of the changes weren't autocorrected and modified logic in e.g. test blocks.

Signatures do not persist when using the GitHub UI "Rebase and merge" button, and --no-upload would still download the bottles. This option prevents downloading the bottles when we simply want to rebase and merge.

[BrewTestBot]

Review period will end on 2021-07-07 at 14:10:21 UTC.

[MikeMcQuaid]

Downloading the bottles and verifying their checksums seems appropriate in this case, no?

Would be great to figure out a way to have this workflow handled by @BrewTestBot instead. Is --autosquash insufficient here?

[nandahkrishna]

Downloading the bottles and verifying their checksums seems appropriate in this case, no?

I don't think so – unless I'm missing something, we aren't updating the bottles here (no revision bump or not necessary to have rebuilt bottles), and they're going to be discarded anyway. The only reason for running CI would be to check whether the changes, for e.g. in test blocks across multiple formulae, were correct/didn't break the test/etc.

Would be great to figure out a way to have this workflow handled by @BrewTestBot instead. Is --autosquash insufficient here?

The intention is to use this with BrewTestBot, perhaps by passing this option to the publish workflow or creating a separate "rebase and merge" workflow. This is independent of (and can be used together with) autosquash, which is concerned with ensuring one commit per formula and rewording commit messages.

BrewTestBot already handles PRs with the CI-syntax-only label just fine – there aren't any bottles, the commits are pushed as-is but signed by BrewTestBot. This option is only useful when:

• The CI-syntax-only label isn't applied because we want to ensure tests pass with the changes.
• The changes do not require new bottles.
• We want the commits to be signed (i.e. have the "verified" symbol) which doesn't happen with the "rebase and merge" button in the UI.

The alternative to this so far has been to just use pr-pull with --no-upload and push the commits to homebrew-core's master branch. This still (unnecessarily) downloads the bottles.

[BrewTestBot]

Review period ended.

[nandahkrishna]

With the latest commit, using the CI-no-bottles label for a PR will mean that bottles aren't published by pr-publish or the workflow. Tests will be run though (since that is handled by the homebrew-core workflow, which I think doesn't need changes to accommodate this).

Edit (forgot to add this): After a brief discussion with Mike on Slack, we agreed that handling this via a PR label was a better solution as it would then be seamlessly integrated with the Publish workflow (and the scheduled publish) without extra work from maintainers (except adding a label to the PR which is far simpler than running pr-publish with an argument).

[MikeMcQuaid]

This is great, makes sense to me!