Refactor commit-msg to reduce redundancies by splitting up the pattern
into the different 'levels'.
For the array the change from /bin/sh to /bin/bash was necessary.
Because of that: Change all `test` occurrences to [[ ]] for performance.
Refactor the script to match my coding style more and update the
comments.
When checking the filenames for non-ASCII characters, check also
renaming of files instead of only additions.
