Cloud Build is a powerful, scalable, and cheap way to run your CI/CD builds, but the triggers have some limitations, like branch exclusions.

For example, perhaps you have triggers to:

1. Build/deploy the tags to production
2. Build/deploy the `master branch to integration
3. Build/test feature branches on NOT master|develop

You can handle cases 1 & 2 with branch and tag triggers, but case 3 requires regex exclusions. Unfortunately, this is not an option in Cloud Build triggers.

Regex Contortions to the Rescue

It’s well know that the solution to a regex problem is always more regex.

So, using some negative classes (a bunch of them actually), we can make a NOT master trigger regex for Cloud Build.

e.g. ^(([^m]|m($|[^a]|a($|[^s]|s($|[^t]|t($|[^e]|e($|[^r]))))))|master.+)¹

Don’t Forget to Match the Entire Branch

Make sure you match the entire branch name, unless you want to match multiple branches.

e.g. “^master$” to match master, not “master”

Otherwise, when Jill checks in her feature branch jill-css-masterpiece, it will automatically get sent to integration or worse ².

Match it like you mean it 😉.