How to override GITHUB_HEAD_REF value on github actions workflow

Trying to upload a saved coverage report from the PR as the master branch coverage inside PR merge github actions event

How could I disable github actions detection or override GITHUB_HEAD_REF value and set it as master branch?

Thank you all in advance for any help.

Using the bash uploader, you can specify -B master. You cannot override GITHUB_* env variables, but we will override the branch name.