Do not cd from vim but directly in the shell in preview commit

I have [this](https://github.com/vheon/dotvim/blob/eeca7006c9e78a70579dc57b7c8ba4ea3f5ee0ef/vimrc#L340-L352) in my vimrc for changing the current working directory and was messing with this functionality. Basically if I had more than one plugin with changes hitting `<Enter>` on a sha of a plugin the diff gets displayed in the preview window but if I then hit `<Enter>` on a sha of a different plugin I read in the preview window an error as if it was trying to `git show 'sha'` in the wrong repo. This should fix it but cannot test it on windows. Can you give it a look?