Add bash completion for docker plugin upgrade

[albers]

Ref #29414
As the corresponding feature will be added in 1.13.1, this PR should go there as well.
Ping @sdurrheimer for zsh completion

Notes for reviewers:
The first non-option is completed as <plugin name:tag>. Completions that include : require __ltrim_colon_completions so that they work on the part after the colon.
The following argument is completed to the available plugin names without the tag, but with a colon appended.

[vdemeester]

LGTM 🐸
/cc @thaJeztah @mlaventure

[mlaventure]

LGTM, but:

This only works on the master.

On the 1.13.1 tag and 1.13.x, bash correctly completes upgrade but afterwards it doesn't complete the available plugins.

@albers if we were to do a 1.13.2 do you know what other commit would need to be cherry-picked into 1.13.x for this to work?

[albers]

@mlaventure For me, the PR works if cherry-picked onto 1.13.x. Maybe you forgot to install a plugin when you checked?

[mlaventure]

hum, I had vieux/sshfs installed. Let me double checked, maybe I had the old binary running.

[albers]

@mlaventure --timeout is nonsense here (though it doesn't harm), I'll fix it in a moment.

[mlaventure]

@albers I have the issue with all the plugin commands that should complete on the plugin names actually.

I tried on top of e5a90d4

[albers]

@mlaventure Maybe #30867?

[albers]

@mlaventure That's really strange. Maybe I'm doing sonething wrong. Here's what I did:

$ git branch
* master
$ git fetch origin 1.13.x
From https://github.com/docker/docker
 * branch            1.13.x     -> FETCH_HEAD
$ git checkout 1.13.x
Branch 1.13.x set up to track remote branch 1.13.x from origin.
Switched to a new branch '1.13.x'
$ git fetch albers completion-plugin-upgrade
From https://github.com/albers/docker
 * branch            completion-plugin-upgrade -> FETCH_HEAD
$ git cherry-pick 2c52ec8403d721e567a7c3c129fc38c650b85ba4
[1.13.x 32428de] Add bash completion for `docker plugin upgrade`
 Date: Wed Feb 8 13:40:13 2017 +0100
 1 file changed, 20 insertions(+)
$ git log --oneline -2
32428de Add bash completion for `docker plugin upgrade`
e5a90d4 Merge pull request #30875 from albers/fix-30858
$ make binary shell BIND_DIR=.

In a separate shell

$ docker exec -ti $(docker ps -lq) dockerd

Back in DIND

root@1af0ae499ea0:~# docker plugin install --grant-all-permissions vieux/sshfs
latest: Pulling from vieux/sshfs
86b5589884b3: Download complete
Digest: sha256:e5e584b1a2d0855d0be5817506e07f774c7c248db42015caa1e605a60c256007
Status: Downloaded newer image for vieux/sshfs:latest
Installed plugin vieux/sshfs

root@1af0ae499ea0:~# docker plugin upgrade <tab>  # works!

[mlaventure]

@albers rebuilt my docker-dev image (I tend to keep them around a while), it seems to work now. Not sure what was wrong.

Let's get this merged :)

[albers]

@mlaventure Thanks! Are you working on Ubuntu?

[mlaventure]

I am yes, still on 14.04.5 though