Introduce compose version command

Signed-off-by: Guillaume Tardif <guillaume.tardif@gmail.com>
Signed-off-by: Nicolas De Loof <nicolas.deloof@gmail.com>

cli/cmd/compose/compose.go

@@ -165,6 +165,7 @@ func Command(contextType string) *cobra.Command {
 		eventsCommand(&opts),
 		portCommand(&opts),
 		imagesCommand(&opts),
+		versionCommand(),
 	)
 
 	if contextType == store.LocalContextType || contextType == store.DefaultContextType {

cli/cmd/compose/version.go

@@ -0,0 +1,64 @@
+/*
+   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 (
+	"fmt"
+	"strings"
+
+	"github.com/spf13/cobra"
+
+	"github.com/docker/compose-cli/cli/formatter"
+	"github.com/docker/compose-cli/internal"
+)
+
+type versionOptions struct {
+	format string
+	short  bool
+}
+
+func versionCommand() *cobra.Command {
+	opts := versionOptions{}
+	cmd := &cobra.Command{
+		Use:   "version",
+		Short: "Show the Docker Compose version information",
+		Args:  cobra.MaximumNArgs(0),
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			runVersion(opts)
+			return nil
+		},
+	}
+	// define flags for backward compatibility with com.docker.cli
+	flags := cmd.Flags()
+	flags.StringVarP(&opts.format, "format", "f", "", "Format the output. Values: [pretty | json]. (Default: pretty)")
+	flags.BoolVar(&opts.short, "short", false, "Shows only Compose's version number.")
+
+	return cmd
+}
+
+func runVersion(opts versionOptions) {
+	displayedVersion := strings.TrimPrefix(internal.Version, "v")
+	if opts.short {
+		fmt.Println(displayedVersion)
+		return
+	}
+	if opts.format == formatter.JSON {
+		fmt.Printf(`{"version":"%s"}\n`, displayedVersion)
+		return
+	}
+	fmt.Printf(`Docker Compose version %s`, displayedVersion)
+}