Using not default ssh key
GIT_SSH_COMMAND="ssh -i ~/.ssh/id_rsa_another" git clone ...
# in project root
git config --local core.sshCommand 'ssh -i ~/.ssh/id_rsa_another'
Reset merge commit
git reset --merge HEAD~1
git reset --merge prev_commit
Using not default ssh key
GIT_SSH_COMMAND="ssh -i ~/.ssh/id_rsa_another" git clone ...
# in project root
git config --local core.sshCommand 'ssh -i ~/.ssh/id_rsa_another'
Reset merge commit
git reset --merge HEAD~1
git reset --merge prev_commit