Add GitHub CI

[adamralph]

• https://github.blog/2019-08-08-github-actions-now-supports-ci-cd/
• https://help.github.com/en/articles/workflow-syntax-for-github-actions
• https://help.github.com/en/articles/events-that-trigger-workflows
• https://help.github.com/en/articles/virtual-environments-for-github-actions
• https://help.github.com/en/articles/contexts-and-expression-syntax-for-github-actions
• https://github.com/MattiasBuelens/checkout-pull-request-merge
• https://stackoverflow.com/questions/57535226/is-there-a-way-to-make-github-ci-build-the-test-merge-of-a-pr-rather-than-the-h
• Checkout the test merge of a PR, rather than the head of the PR branch actions/checkout#15
• Sent GitHub support request to get env var added for PR number - ticket # 353792
• https://developer.github.com/v3/repos/commits/#list-pull-requests-associated-with-commit

  you probably need to add a check on head.label to make sure it is not your default branch and you are good

• https://jira.atlassian.com/browse/BSERV-10279

  GitHub calls a "synchronize" event, and includes the pull request details including the new head commit sha for merging

  • https://github.com/bradleyfalzon/gopherci/blob/0eb6aec3ca1a4c1f325573399d0b8c912963502c/internal/github/handlers.go#L180
• https://github.com/SQLStreamStore/SQLStreamStore.Docker/pull/96/files
• https://help.github.com/en/articles/about-actions