All the tests pass. As discussed @kencochrane I'll wait for confirmation that real-world usage works for a couple people other than you and me.

Let me know!

I gave it a shot. Two issues...

The first one is minor: docker help login actually invokes CmdLogin and doesn't return any help information. Try adding the following to the top:

if err := cmd.Parse(args); err != nil {
    return nil
}

With the second one, I was able to reproduce Solomon's issues, with a little more detail:

$ docker login # First time ...
...
$ docker login # Enter at prompt...
Error: Registration: 
$ docker login # Enter at prompt...
Error : use of closed network connection

I did some testing with strace -f -s 1024 docker login and found that:

• When you receive Error : Registration:, it happens when the server returns an HTTP 400
• When you receive Error : use of closed network connection, the server has returned an HTTP 200

More information about the Error : use of closed network connection error... when this happens, it appears as if the read is cut short (or maybe the write is, I can't tell). Here is the actual system call (which is actually multiple read() calls, formatted for readability:

[pid  4247] read(51, "
    HTTP/1.1 200 OK\r\n
    server: gunicorn/0.17.2\r\n
    date: Fri, 15 Mar 2013 06:40:55 GMT\r\n
    connection: close\r\n
    expires: -1\r\n
    content-type: text/plain\r\n
    pragma: no-cache\r\n
    cache-control: no-cache\r\n
    content-length: 2\r\n
    \r\n", 4096) = 201

And here's a response from a Login succeeded message:

[pid  4342] read(51, "
    HTTP/1.1 200 OK\r\n
    server: gunicorn/0.17.2\r\n
    date: Fri, 15 Mar 2013 06:41:24 GMT\r\n
    connection: close\r\n
    expires: -1\r\n
    content-type: text/plain\r\n
    pragma: no-cache\r\n
    cache-control: no-cache\r\n
    content-length: 2\r\n
    \r\n
    ok", 4096) = 203

At first glance they look very similar, but in the error case, the body of "ok" is never received.

I gave it a shot:

• Minor issues:
  • We can create an account with an empty password
• Improvements:
  • Hide the password while we type it

Otherwise, it looks good (beside the issues cited by Charles which are very annoying)

I fixed the issue with no password, and the help message

Any problems left?

We were able to reproduce, it was actually a server issue not a client issue. We are changing the server to fix. this should be good to merge.

Replaced the server by uwsgi. Ready to be retried!