Tagging just once against a branch works!
example usage:
export TYG_TAGS='[{"patterns":["content/*"],"tags":["content-changed"]}]'
export TYG_GIT_API_KEY=big-ol-key
export TYG_ENTERPRISE_URL=https://github.internal.com/api/v3
tyg tag -pr=https://github.internal.com/org/repo/pull/10