docs/data/reusables/pages/pages-about-branch-source.md

You can specify which branch and folder to use as your publishing source. The source branch can be any branch in your repository, and the source folder can either be the root of the repository (/) on the source branch or a /docs folder on the source branch. Whenever changes are pushed to the source branch, the changes in the source folder will be published to your {% data variables.product.prodname_pages %} site.