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How do you do it? Because I'm planning on doing it when adding new TMs to my hack.
Can you please provide more details on your normal workflow? Are you editing the repo files via GitHub web interface only?
Using git (the CLI program), you'd create a branch this way:
git branch name-of-my-new-branch # create your new branch git checkout name-of-my-new-branch # move to the branch you just created
Or, in a single command:
git checkout -b name-of-my-new-branch