Unclear prompt for SSH private key passphrase

[ncoghlan]

When using DA to create a new GitHub repo, it wasn't immediately obvious why a prompt had come up to request my passphrase for SSH private key access, so I denied it access.

The project setup otherwise worked, so the only change I had to make was to git push --set-upstream origin master from the terminal after adding my ssh keys to the session.

Given #386, credential management in general may be worth revisiting (and I presume may be affected by the work to switch DA to a client/server architecture)