如何强制composer重新安装一个库?

I'm using the ZF2 skeleton app and it has a .gitignore that prevents external libraries from being commited to git. While debugging I like to go and change stuff here and there in the libraries' source to learn how things work. If these were version controlled it would be very easy to revert them back to their original state.I'm using the ZF2 skeleton app and it has a .gi