If you are getting
$ git clone firstname.lastname@example.org:worp1900/my-project.git Cloning into 'my-project'... The server's host key is not cached in the registry. You have no guarantee that the server is the computer you think it is. The server's rsa2 key fingerprint is: ssh-rsa 2048 github:key If you trust this host, enter "y" to add the key to PuTTY's cache and carry on connecting. If you want to carry on connecting just once, without adding the key to the cache, enter "n". If you do not trust this host, press Return to abandon the connection. Store key in cache? (y/n) y
This gives you a deadlock situation as Windows will not allow you to enter “y” and accept the host key. You will be stuck in this screen forever.
How to solve?
Check out the solution on github: Git clone / pull continually freezing at “Store key in cache?”
Simply use putty to quickly ssh connect to the remote github server (unsuccessfully obvsiouly). But putty will register the host key with your system. When you git clone afterwards, the host key is know and clone will work.