Using Different Key for GitHub Push

If your default id_rsa key is different than the one you use for GitHub, it’s still possible to use simple git push regardless. Trick is in adding mapping to identity file in ~/.ssh/config:

Host github.com
  User git
  IdentityFile ^^~/.ssh/id_rsa_github^^
  IdentitiesOnly yes

This will ensure all communication with github.com uses id_rsa_github key.