I recently registered on heroku with my work email address : firstname.lastname@example.org (obsfuscated)
My ssh id_dsa though is signed with my personal email address : email@example.com.
Heroku doesn’t like this one bit.
Following this advice, I created id_heroku_rsa wtih my work-email comment.
Still no-joy. But, this StackOverflow thread left a clue… using the ssh debugging output, I can see that ssh is still trying to send id_rsa or id_dsa.
The answer, included on that post is to ‘ssh-add’ the special key created.
Voila, now my push succeeds.