Fix short write (#28)

* session: pty normalization hack needs to return expected bytes written or chaos ensues, such as short write errors
* _example: renaming to avoid editors that auto-install from making docker binaries in your path that aren't docker
* session: keep extra calculations limited to pty case

Signed-off-by: Jeff Lindsay <progrium@gmail.com>

_example/ssh-docker/docker.go

@@ -74,7 +74,7 @@ func dockerRun(cfg *container.Config, sess ssh.Session) (err error, status int64
 	go func() {
 		var err error
 		if cfg.Tty {
-			_, err = io.Copy(sess, stream.Conn)
+			_, err = io.Copy(sess, stream.Reader)
 		} else {
 			_, err = stdcopy.StdCopy(sess, sess.Stderr(), stream.Reader)
 		}

session.go

@@ -65,9 +65,16 @@ type session struct {
 
 func (sess *session) Write(p []byte) (n int, err error) {
 	if sess.pty != nil {
-		// normalize \n to \r\n when pty is accepted
+		m := len(p)
+		// normalize \n to \r\n when pty is accepted.
+		// this is a hardcoded shortcut since we don't support terminal modes.
 		p = bytes.Replace(p, []byte{'\n'}, []byte{'\r', '\n'}, -1)
 		p = bytes.Replace(p, []byte{'\r', '\r', '\n'}, []byte{'\r', '\n'}, -1)
+		n, err = sess.Channel.Write(p)
+		if n > m {
+			n = m
+		}
+		return
 	}
 	return sess.Channel.Write(p)
 }