In some cases you may need to build when a pull request is opened and when a commit is pushed to every branch.
Building on Pull Requests
In order to build when a pull request is opened, you will need to enable the Only build pull requests feature. Enabling this feature will build when a PR is opened and to commits to your default branch.
Adding default branches
You can view your projects default branch branch by using the get a Project API endpoint: https://circleci.com/docs/api/v2/index.html#tag/Project
You may add additional default branches by leveraging the CircleCI API as mentioned in the following support article: https://support.circleci.com/hc/en-us/articles/15222074173723-How-to-allowlist-additional-branches-for-Only-Build-Pull-Requests
To add all branches as default branches, please add "*" as a default branch. For example: