Introducing SSH Remote Mirroring in git-sync

Git-sync 0.5.0 introduces SSH Remote Mirroring, allowing users to mirror Git repositories using SSH access without switching to HTTPS, thereby maintaining existing SSH configurations. This feature supports mirroring from ssh:// URLs, SCP-style URLs, and between mixed transport methods, such as an HTTPS source and an SSH target, which is particularly useful for handling private repositories, preserving host aliases, and managing different access methods. The SSH remotes utilize the local SSH binary in batch mode, though they currently do not provide SSH byte-counted transfer metrics in --progress and --stats outputs. Users can implement this by running git-sync with an SSH source or target URL to sync repositories seamlessly.