cmd/juju: Improvements and minor fixes to ssh/scp

cmd/juju: Improvements and minor fixes to ssh/scp

This CL mostly deals with suggestions from the last
review (https://codereview.appspot.com/66340045/),
which arrived after landing.

Summary of the changes:
 - scp using go.crypto has a better error message;
 - scp now accepts extra args last only, and no need for --;
 - scp works correctly with nodes that have public IPv6 address;
 - improved and rephrased help text for scp.

https://code.launchpad.net/~dimitern/juju-core/303-ssh-scp-improvements/+merge/207986

(do not edit description out of merge proposal)

[dimitern, 2014-02-24 17:29:05]

Please take a look.

[natefinch, 2014-02-24 17:44:25]

LGTM

https://codereview.appspot.com/67820048/diff/1/utils/ssh/ssh.go
File utils/ssh/ssh.go (right):

https://codereview.appspot.com/67820048/diff/1/utils/ssh/ssh.go#newcode72
utils/ssh/ssh.go:72: // Copy copies file(s) between local and/ remote host(s).
remove the errant slash?

[dimitern, 2014-02-24 17:52:35]

Please take a look.

https://codereview.appspot.com/67820048/diff/1/utils/ssh/ssh.go
File utils/ssh/ssh.go (right):

https://codereview.appspot.com/67820048/diff/1/utils/ssh/ssh.go#newcode72
utils/ssh/ssh.go:72: // Copy copies file(s) between local and/ remote host(s).
On 2014/02/24 17:44:26, nate.finch wrote:
> remove the errant slash?

Done.

[axw, 2014-02-25 02:23:53]

Thanks for the updates and improvements. Sorry for harping on, but there's still
a couple of issues.

https://codereview.appspot.com/67820048/diff/20001/cmd/juju/scp.go
File cmd/juju/scp.go (left):

https://codereview.appspot.com/67820048/diff/20001/cmd/juju/scp.go#oldcode83
cmd/juju/scp.go:83: if v := strings.SplitN(arg, ":", 2); len(v) > 1 {
I think the BUG was actually about this line. Say you do

    juju scp 0:/local/file [::1]:/tmp

Then the SplitN won't do the right thing.

https://codereview.appspot.com/67820048/diff/20001/cmd/juju/scp.go
File cmd/juju/scp.go (right):

https://codereview.appspot.com/67820048/diff/20001/cmd/juju/scp.go#newcode94
cmd/juju/scp.go:94: host = fmt.Sprintf(`\[%s\]`, host)
Escaping the square brackets here doesn't seem right. That should be up to the
client implementation.

https://codereview.appspot.com/67820048/diff/20001/cmd/juju/scp_test.go
File cmd/juju/scp_test.go (right):

https://codereview.appspot.com/67820048/diff/20001/cmd/juju/scp_test.go#newco...
cmd/juju/scp_test.go:40: []string{"0:foo", ".", "-rv -o SomeOption"},
This isn't really testing reality is it? Shouldn't that be "-rv", "-o",
"SomeOption"? Otherwise you're testing the equivalent of someone running, on the
command line:
    juju scp 0:foo . '-rv -o SomeOption'

If "-o" and "SomeOption" were separate args, as would be the norm, you'll see
the problem I mentioned.