GitWorkingCopy::add() or rm() didn't work as expected due escaping strategy

if you run commands like $workingCopy->add('path/to/file.txt') files was never staged within the git repository (checked manually with git status). 
A while of debugging shows, that the file-extension escaping strategy caused the issue. If you run $workingCopy->run('add', 'path/to/file.txt') without escaping the file through the GitCommand::escapeFilepattern() method, adding (or similar rm() ) works as expected.