Summary:
When saving a changed pipeline to a new branch in GitHub, the editor allows the user to provide a branch name with spaces in it.

Steps to recreate:
1. Edit an existing, functional pipeline with the editor. Make a trivial change.

2. Click Save.

3. Add a description, and select "Commit to new branch."

4. Provide a branch name that contains spaces.

5. Click "Save and run." You'll get "Error: Bad Request" when you try this.

6. Remove the spaces from the branch name, and everything works fine.

This isn't a high severity issue, but it seems like some field controls preventing users from trying to use spaces in their branch names might be helpful.