Fix #18
Fix #18

Avoid creating strings with weird characters by using a git format that
only outputs an abbreviated commit hash.

fimmtiu/rubycritic,whitesmith/rubycritic,bglusman/rubycritic,bglusman/rubycritic,ancorgs/rubycritic,whitesmith/rubycritic,fimmtiu/rubycritic,whitesmith/rubycritic,whitesmith/rubycritic,fimmtiu/rubycritic,ancorgs/rubycritic,bglusman/rubycritic,ancorgs/rubycritic