You can require people to resolve merge conflicts locally by disabling the merge conflict editor on GitHub Enterprise for pull requests where the base branch and the head branch are in different repositories.
Requiring users to resolve merge conflicts locally on their computer can prevent people from inadvertently writing to an upstream repository from a fork.
Sign in to your GitHub Enterprise instance at
In the left sidebar, click Admin center.
Under "Conflict editor for pull requests between repositories," select Disabled or Enabled.