This answer is primarily for windows users and also equally relevant if you're having trouble cloning with tfs, github or gitlab on any other OS.
The default authentication mode when using SSH is the private key. Whenever that fails for some reason, the ssh-agent falls back to username and password based authentication.
There are several reasons why the default key based authentication might have failed. Following are the most common cases :
a) The ssh-agent cannot find the default private key file which is id_rsa, and no other key path is specified explicitly.
b) The public key stored in the server is incorrect.
c) The path you're trying to clone is incorrect.
In any case, to troubleshoot the issue, first of all execute the git clone command with verbose logging with the command :
GIT_TRACE=1 GIT_SSH_COMMAND="ssh -vvv" git clone ssh://pathToYourRepo
You can go through each step in the log to get an intuition of what the issue might be.
Troubleshooting in case of (a)
Make sure you have the default key name id_rsa in the .ssh directory. You might have specified some different keyname when generating the key with ssh-keygen command or maybe there isn't any key at all).
In case you want to specify a different key for authentication, use the following command :
ssh-agent bash -c 'ssh-add ~/.ssh/anotherKey; git clone ssh://pathToYourRepo'
Troubleshooting in case of (b)
- Make sure there aren't extra white spaces when storing the public key in the server.
Troubleshooting in case of (c)
- Make sure you aren't trying to clone with the https version of the repository path.