Add option to ignore moved/deleted files

[Svenito]

Is your feature request related to a problem? Please describe.
It should be possible to ignore moved or deleted files when determining if they should be formatted. We only care about formatting if code as been touched inside the file, not if the file has been moved or deleted.

Describe the solution you'd like
Add a new option to only process files that have had their content changed

Additional context
This could be done by adding --diff-filter=M to the _git_diff_name_only function if the command line flag is set