Add shell completion

[booyaa]

This is my attempt to implement #1308.

Out of the box codegangsta's cli package supports command completion, but not flags (global or command specific) there's a pending enhancement request urfave/cli#188. So I've decided to implement this and maybe give back to the cli package too!

I've been playing around with the config and create commands.

So far I've been unable to access the Flags of commands. I can display the global flags (in app.Flags), but this also has the undesired effect of display aliases and (I think) descriptions of the flags.

[booyaa@hodor machine GO  (add_shell_completion) ] $ ./docker-machine_darwin-amd64 config<tab>
(Go-based)                     -s,                            auth                           path
--debug,                       -v                             cert                           print
--generate-bash-completion     /Users/booyaa/.docker/machine  certificates                   remotes
--help,                        CA                             client                         show
--native-ssh                   Client                         debug                          storage
--storage-path                 Configures                     for                            the
--tls-ca-cert                  Enable                         generate                       to
--tls-ca-key                   Private                        help                           use
--tls-client-cert              SSH                            implementation.                used
--tls-client-key               TLS                            in                             verify
--version,                     Use                            key                            version
-D                             []                             mode
-h                             against                        native

I've added the stock shell completion script in the script folder, but whilst writing the issue #1308 I discovered the completion scripts in docker and compose live in a contrib folder, so I'll move it there.

Usage of the completion script is as follows:

PROG=docker-machine_os_arch source=script/machine

The script can be tailored to predefine PROG as docker-machine

Finally any suggestions on any part of this PR (in particular testing) are appreciated. I'm still fairly new to Go, but always willing to learn.

[ehazlett]

Thanks for the contribution! The output looks a little odd. For example, there is [] and Use, for, generate, implementation, etc. Those are not valid commands. I'm also not sure about having the flags in -- it makes the output a little confusing but that's just me.

[booyaa]

Yeah definitely think the [] and other bits are artifacts from the flags array. I'll scale it back to commands initially and move the script to a contrib directory.

Testing should be really easy then, just need to compare the output from the --enable-bash-completion with the commands array.

[hairyhenderson]

hey @booyaa - you'll need to sign your commits and re-push for the build to pass

[booyaa]

heya @hairyhenderson i'm probably going to rollback the changes to commands/commands.go to the commit before mine. what's the prefer way to sync my changes? close and raise new pr, or just push updates back to master?

[nathanleclaire]

We've merged in #1993 so I'm going to close this.