Implement some small improvements to export_mc (#2948)
Implement some small improvements to export_mc (#2948)

Add --no-commit option, so you can preview the changes without causing a commit
Validate --branch or --no-switch-branch options
Make it valid Python 3 (and Python 2), even though we aren't using Python 3, because my editor for unrelated reasons is now linting everything as Python 3.
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