cmd: add helloworld example

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

cmd/buildx/main.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/docker/cli/cli-plugins/manager"
+	"github.com/docker/cli/cli-plugins/plugin"
+	"github.com/docker/cli/cli/command"
+	"github.com/spf13/cobra"
+	"github.com/tonistiigi/buildx/version"
+)
+
+func main() {
+	plugin.Run(func(dockerCli command.Cli) *cobra.Command {
+		goodbye := &cobra.Command{
+			Use:   "goodbye",
+			Short: "Say Goodbye instead of Hello",
+			Run: func(cmd *cobra.Command, _ []string) {
+				fmt.Fprintln(dockerCli.Out(), "Goodbye World!")
+			},
+		}
+		apiversion := &cobra.Command{
+			Use:   "apiversion",
+			Short: "Print the API version of the server",
+			RunE: func(_ *cobra.Command, _ []string) error {
+				cli := dockerCli.Client()
+				ping, err := cli.Ping(context.Background())
+				if err != nil {
+					return err
+				}
+				fmt.Println(ping.APIVersion)
+				return nil
+			},
+		}
+
+		exitStatus2 := &cobra.Command{
+			Use:   "exitstatus2",
+			Short: "Exit with status 2",
+			RunE: func(_ *cobra.Command, _ []string) error {
+				fmt.Fprintln(dockerCli.Err(), "Exiting with error status 2")
+				os.Exit(2)
+				return nil
+			},
+		}
+
+		var (
+			who, context  string
+			preRun, debug bool
+		)
+		cmd := &cobra.Command{
+			Use:   "helloworld",
+			Short: "A basic Hello World plugin for tests",
+			PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
+				if err := plugin.PersistentPreRunE(cmd, args); err != nil {
+					return err
+				}
+				if preRun {
+					fmt.Fprintf(dockerCli.Err(), "Plugin PersistentPreRunE called")
+				}
+				return nil
+			},
+			RunE: func(cmd *cobra.Command, args []string) error {
+				if debug {
+					fmt.Fprintf(dockerCli.Err(), "Plugin debug mode enabled")
+				}
+
+				switch context {
+				case "Christmas":
+					fmt.Fprintf(dockerCli.Out(), "Merry Christmas!\n")
+					return nil
+				case "":
+					// nothing
+				}
+
+				if who == "" {
+					who, _ = dockerCli.ConfigFile().PluginConfig("helloworld", "who")
+				}
+				if who == "" {
+					who = "World"
+				}
+
+				fmt.Fprintf(dockerCli.Out(), "Hello %s!\n", who)
+				dockerCli.ConfigFile().SetPluginConfig("helloworld", "lastwho", who)
+				return dockerCli.ConfigFile().Save()
+			},
+		}
+
+		flags := cmd.Flags()
+		flags.StringVar(&who, "who", "", "Who are we addressing?")
+		flags.BoolVar(&preRun, "pre-run", false, "Log from prerun hook")
+		// These are intended to deliberately clash with the CLIs own top
+		// level arguments.
+		flags.BoolVarP(&debug, "debug", "D", false, "Enable debug")
+		flags.StringVarP(&context, "context", "c", "", "Is it Christmas?")
+
+		cmd.AddCommand(goodbye, apiversion, exitStatus2)
+		return cmd
+	},
+		manager.Metadata{
+			SchemaVersion: "0.1.0",
+			Vendor:        "Docker Inc.",
+			Version:       version.Version,
+		})
+}

version/version.go

@@ -0,0 +1,13 @@
+package version
+
+var (
+	// Package is filled at linking time
+	Package = "github.com/tonistiigi/buildx"
+
+	// Version holds the complete version number. Filled in at linking time.
+	Version = "0.0.0+unknown"
+
+	// Revision is filled with the VCS (e.g. git) revision being used to build
+	// the program at linking time.
+	Revision = ""
+)