Git and SSH, which key is used?

Question

Say your .ssh directory contains 30 keys (15 private and 15 public).

Where in Git can one check which one is used to connect to a given remote repository?

Answer 1

This might be super edge, but after running ssh -vT git@github.com it showed me it was checking /root/.ssh for the keys, I was expecting it to check my home directory and then I realized I was logged in as root!