Slightly relax the conditions under which an error is considered to
indicate that the SSH agent is not running, to accommodate differences
in the API of named pipes on Windows vs. Unix domain sockets.
The trait `radicle_ssh::agent::client::ClientStream` trait was
simplified, because `winpipe::WinStream` is so similar to
`std::os::unix::net::UnixStream` that we can just use the same
implementation for both platforms.
However, obtaining the process identifier of the SSH agent process is
not common on Windows, so we instead track the path that we used to
connect to the agent. This is also helpful on Unix. In some cases, the
path will even contain the process identifier. The path is printed by
`rad self`.
Errors are cleaned up, and error messages are improved.
Lorenz Leutgeb
Yaroslav Halchenko
Lorenz Leutgeb
Fintan Halpenny