Configure Cirrus Branch Guard

[amirh]

Description

This should add a presubmit that's block PR from landing while the tree is red.

Related Issues

flutter/flutter#28921

[amirh]

@fkorotkov

[fkorotkov]

Actions picks configs from master and not the current branch. So once it's merged you'll the action in action. 😅

[amirh]

@fkorotkov I just submitted a new PR to test this, it seems like something isn't configured properly:

https://github.com/flutter/plugins/pull/2493/checks?check_run_id=424083286

 Run cirrus-actions/branch-guard@v1.21s
##[error]Node run failed with exit code 1
Run cirrus-actions/branch-guard@v1.2
[@octokit/rest] `const Octokit = require("@octokit/rest")` is deprecated. Use `const { Octokit } = require("@octokit/rest")` instead
[@octokit/rest] `const Octokit = require("@octokit/rest")` is deprecated. Use `const { Octokit } = require("@octokit/rest")` instead
[@octokit/rest] `const Octokit = require("@octokit/rest")` is deprecated. Use `const { Octokit } = require("@octokit/rest")` instead
Handling 'opened' action for pull_request event for refs/pull/2493/merge@685883f27477af9021590562a92b25cc6d630235.
Checking reference master for PR #2493 and SHA 3ee9504e572b2273210b65a0f47d2dc9f6a0cc5b.
Check suite 435935103: Cirrus CI in_progress null
Check suite 435935105: WIP queued null
Check suite 435949935: GitHub Actions completed skipped
Processing 1 check suites after filtering by 'appsToCheck'.
##[error]Resource not accessible by integration
##[error]Node run failed with exit code 1

[fkorotkov]

Damn, it seems it's failing because the PR comes from a fork and the action is authorized with permissions of a fork which can't update status checks. Seems it's a limitation that can't be workarounded and we'll need to incorporate the logic in Cirrus or a separate GitHub App. For now it seems we can keep triggering the action on check_suite but then newly created PRs won't get an update until a new commit is merged to master.

[amirh]

Bummer.

Only updating when a commit is merged to master will deadlock the branch once it's red won't it?

Should I revert this PR for now?

[fkorotkov]

Yeah, once a branch is red your'll need to merge though the red branch-guard check in order to fix it for all other PRs. Please revert or check #2495