Implement a helper function for sudo.

Implement a helper function for sudo.

Most of the local plugin helper commands will need
to run as sudo. Instead of each writing their own
code to handle this, provide a helper function.

https://code.launchpad.net/~thumper/juju-core/local-ensure-root/+merge/211849

(do not edit description out of merge proposal)

[thumper, 2014-03-20 02:04:37]

Please take a look.

[wallyworld, 2014-03-20 03:11:28]

LGTM with suggestion considered

https://codereview.appspot.com/78030044/diff/1/cmd/plugins/local/main.go
File cmd/plugins/local/main.go (right):

https://codereview.appspot.com/78030044/diff/1/cmd/plugins/local/main.go#newc...
cmd/plugins/local/main.go:48: func ensureRoot(args []string, context
*cmd.Context, call func(*cmd.Context) error) error {
Even though not exported, a doc comment would be nice. Maybe include that args
contains cmd to run in args[0] etc. I think I'd prefer args split up so that
command is passed in explicitly

func ensureRoot(cmd string, cmdArgs []string, context *cmd.Context, call
func(*cmd.Context) error {
}

And maybe call the method runAsRoot()