Fix git bash detection and path to the tar file (#271)

* `ulimit` does not work but `uname` does.
* Fixed the `c:\path\to\file` to `/c/path/to/file` conversion.
* The path adjustment only applies to the `tar` command. It'll cause problems later on if left as `/c/path/to/file`.

This should at least work in Git Bash, and, so long as Git is added to the `PATH`, it'll work via Windows cmd too.