How can you use PyCharm with multiple SSH identities?

I have two different ssh identities for the same Git-based VCS, one for each repo that I have there. How can I get PyCharm to use the proper id_rsa file for each? Whenever I perform a VCS operation, PyCharm prompts for a passphrase, but there's no way (that I can find) to tell PyCharm which key file I want to use. It just defaults to the one named id_rsa. I can play games with symbolic links and ensure ahead of time that id_rsa is linked to the file I want to use, but is there a way to either associate a key file with a repo or make that choice interactively?

Apologies if a duplicate – searched and didn't find this question.

Thanks.