Add completion to shells

Signed-off-by: Ulysses Souza <ulyssessouza@gmail.com>

cli/cmd/compose/completion.go

@@ -0,0 +1,86 @@
+/*
+   Copyright 2020 Docker Compose CLI authors
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package compose
+
+import (
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+func completionCommand() *cobra.Command {
+	return &cobra.Command{
+		Use:   "completion [bash|zsh|fish|powershell]",
+		Short: "Generate completion script",
+		Long: `To load completions:
+
+Bash:
+
+  $ source <(docker compose completion bash)
+
+  # To load completions for each session, execute once:
+  # Linux:
+  $ docker compose completion bash > /etc/bash_completion.d/docker_compose
+  # macOS:
+  $ docker compose completion bash > /usr/local/etc/bash_completion.d/docker_compose
+
+Zsh:
+
+  # If shell completion is not already enabled in your environment,
+  # you will need to enable it.  You can execute the following once:
+
+  $ echo "autoload -U compinit; compinit" >> ~/.zshrc
+
+  # To load completions for each session, execute once:
+  $ docker compose completion zsh > "${fpath[1]}/_docker_compose"
+
+  # You will need to start a new shell for this setup to take effect.
+
+fish:
+
+  $ docker compose completion fish | source
+
+  # To load completions for each session, execute once:
+  $ docker compose completion fish > ~/.config/fish/completions/docker_compose.fish
+
+PowerShell:
+
+  PS> docker compose completion powershell | Out-String | Invoke-Expression
+
+  # To load completions for every new session, run:
+  PS> docker compose completion powershell > docker_compose.ps1
+  # and source this file from your PowerShell profile.
+`,
+		DisableFlagsInUseLine: true,
+		ValidArgs:             []string{"bash", "zsh", "fish", "powershell"},
+		Args:                  cobra.ExactValidArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			var err error
+			switch args[0] {
+			case "bash":
+				err = cmd.Root().GenBashCompletion(os.Stdout)
+			case "zsh":
+				err = cmd.Root().GenZshCompletion(os.Stdout)
+			case "fish":
+				err = cmd.Root().GenFishCompletion(os.Stdout, true)
+			case "powershell":
+				err = cmd.Root().GenPowerShellCompletion(os.Stdout)
+			}
+			return err
+		},
+	}
+}

cmd/compose/compose.go

@@ -41,10 +41,10 @@ import (
 	"github.com/docker/compose-cli/pkg/compose"
 )
 
-//Command defines a compose CLI command as a func with args
+// Command defines a compose CLI command as a func with args
 type Command func(context.Context, []string) error
 
-//Adapt a Command func to cobra library
+// Adapt a Command func to cobra library
 func Adapt(fn Command) func(cmd *cobra.Command, args []string) error {
 	return func(cmd *cobra.Command, args []string) error {
 		ctx := cmd.Context()
@@ -276,6 +276,7 @@ func RootCommand(contextType string, backend api.Service) *cobra.Command {
 		portCommand(&opts, backend),
 		imagesCommand(&opts, backend),
 		versionCommand(),
+		completionCommand(),
 	)
 
 	if contextType == store.LocalContextType || contextType == store.DefaultContextType {