Added version sub-command

Author: skx

cmd_version.go

@@ -0,0 +1,59 @@
+//
+// Show our version.
+//
+
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"runtime"
+
+	"github.com/google/subcommands"
+)
+
+var (
+	version = "unreleased"
+)
+
+type versionCmd struct {
+	verbose bool
+}
+
+//
+// Glue
+//
+func (*versionCmd) Name() string     { return "version" }
+func (*versionCmd) Synopsis() string { return "Show our version." }
+func (*versionCmd) Usage() string {
+	return `version :
+  Report upon our version, and exit.
+`
+}
+
+//
+// Flag setup
+//
+func (p *versionCmd) SetFlags(f *flag.FlagSet) {
+	f.BoolVar(&p.verbose, "verbose", false, "Show go version the binary was generated with.")
+}
+
+//
+// Show the version - using the "out"-writer.
+//
+func showVersion(verbose bool) {
+	fmt.Printf("%s\n", version)
+	if verbose {
+		fmt.Printf("Built with %s\n", runtime.Version())
+	}
+}
+
+//
+// Entry-point.
+//
+func (p *versionCmd) Execute(_ context.Context, f *flag.FlagSet, _ ...interface{}) subcommands.ExitStatus {
+
+	showVersion(p.verbose)
+	return subcommands.ExitSuccess
+}

main.go

@@ -23,6 +23,7 @@ func main() {
 	subcommands.Register(&lexCmd{}, "")
 	subcommands.Register(&parseCmd{}, "")
 	subcommands.Register(&runCmd{}, "")
+	subcommands.Register(&versionCmd{}, "")
 
 	flag.Parse()
 	ctx := context.Background()