Add bash completion for available plugins

[crazy-max]

closes #4089

- What I did

This is a follow-up of #4089 (comment) to enable bash completion for available plugins.

- How I did it

- How to verify it

$ mkdir -p ~/.local/share/bash-completion/completions
$ cp ./contrib/completion/bash/docker ~/.local/share/bash-completion/completions/docker
$ _completion_loader docker

$ docker info --format '{{json .ClientInfo.Plugins}}' | jq
[
  {
    "SchemaVersion": "0.1.0",
    "Vendor": "Docker Inc.",
    "Version": "v0.10.0-rc2-175-g00bb9c5c.m",
    "ShortDescription": "Docker Buildx",
    "Name": "buildx",
    "Path": "/home/crazy/.docker/cli-plugins/docker-buildx",
    "ShadowedPaths": [
      "/usr/libexec/docker/cli-plugins/docker-buildx"
    ]
  },
  {
    "SchemaVersion": "0.1.0",
    "Vendor": "Docker Inc.",
    "Version": "v2.16.0",
    "ShortDescription": "Docker Compose",
    "Name": "compose",
    "Path": "/usr/libexec/docker/cli-plugins/docker-compose"
  },
  {
    "SchemaVersion": "0.1.0",
    "Vendor": "Docker Inc.",
    "Version": "v0.23.0",
    "ShortDescription": "Docker Scan",
    "Name": "scan",
    "Path": "/usr/libexec/docker/cli-plugins/docker-scan"
  }
]

$ docker build [tab][tab]
build    builder  buildx

$ docker buildx [tab][tab]
bake        create      help        inspect     prune       stop        version     
build       du          imagetools  ls          rm          use

$ docker buildx b [tab][tab]
bake   build

$ docker co [tab][tab]
commit     compose    config     container  context

$ docker compose [tab][tab]
build    cp       down     exec     kill     ls       port     pull     restart  run      stop     unpause  version  
config   create   events   images   logs     pause    ps       push     rm       start    top      up

To make it works with buildx plugin you need docker/buildx#1674

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

cc @silvin-lubecki @ulyssessouza

[silvin-lubecki]

Not a shell script expert here, but the logic looks good 👍

[albers]

This is really, really cool.

I have to admit that I do not fully understand __docker_complete_plugin() but I assume this is basically an idiom for cobra generated completions and should be correct.

I did not find any issues with the completions.

Thanks @crazy-max.

[crazy-max]

@albers Thanks for the review. I made the suggested changed.

I think in follow-up we could use the same logic but for all docker commands so we would only need a single function to handle completion like the __docker_complete_plugin() one does.

I also have a branch to handle this for fish and zsh.

e.g., for fish:

# plugins
set PLUGINS_PATH (docker info --format '{{range .ClientInfo.Plugins}}{{.Path}},{{end}}')

function __fish_docker_plugin_complete --description 'Print plugins commands and subcomands' -a plugin_path
    set -l resultArray $plugin_path "__completeNoDesc"
    for i in (commandline -opc)
        if set -q i
            set -a resultArray "''"
        else
            set -a resultArray $i
        end
    end
    set -l result (eval printf '%s ' $resultArray 2> /dev/null | grep -v '^:[0-9]*$')
    if set -q i
        return 1
    end
    echo $result
    return 0
end

for plugin_path in (string split ',' $PLUGINS_PATH)
    set plugin_name (string trim $plugin_path)
    set plugin_name (string trim -l 'docker-' $plugin_name)
    set plugin_name (echo $plugin_name | sed 's/\.[^.]*$//')
    complete -c docker -f -n '__fish_docker_no_subcommand' -a $plugin_name
    complete -c docker -A -f -n "__fish_seen_subcommand_from $plugin_name" -a "(__fish_docker_plugin_complete $plugin_path)"
end

Not tested and needs more work I think. I'm not an expert of this shell 😅.

[codecov-commenter]

Codecov Report

Merging #4094 (aa0aa4a) into master (cb5463a) will decrease coverage by 0.02%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4094      +/-   ##
==========================================
- Coverage   59.15%   59.13%   -0.02%     
==========================================
  Files         285      285              
  Lines       24725    24738      +13     
==========================================
+ Hits        14627    14630       +3     
- Misses       9212     9221       +9     
- Partials      886      887       +1     

[albers]

Thanks @crazy-max. Very impressive.

[crazy-max]

PTAL @thaJeztah @vvoland 🙏

[vvoland]

Just tested and it seems to work perfectly, thanks!

[ulyssessouza]

LGTM! 🥳

[thaJeztah]

LGTM