Remove lightstep configuration

The `github.com/shirou/gopsutil` dependency of lightstep-tracer is
giving us trouble during building.

Ref. https://github.com/shirou/gopsutil/issues/976

Another build problem raises its head even after we upgrade gopsutil to
a version where the above bug is fixed.

cmd/ghcs/root.go

@@ -1,21 +1,12 @@
 package ghcs
 
 import (
-	"fmt"
-	"log"
-	"strconv"
-	"strings"
-
-	"github.com/lightstep/lightstep-tracer-go"
-	"github.com/opentracing/opentracing-go"
 	"github.com/spf13/cobra"
 )
 
 var version = "DEV" // Replaced in the release build process (by GoReleaser or Homebrew) by the git tag version number.
 
 func NewRootCmd(app *App) *cobra.Command {
-	var lightstep string
-
 	root := &cobra.Command{
 		Use:           "ghcs",
 		SilenceUsage:  true,  // don't print usage message after each error (see #80)
@@ -25,14 +16,8 @@ func NewRootCmd(app *App) *cobra.Command {
 Running commands requires the GITHUB_TOKEN environment variable to be set to a
 token to access the GitHub API with.`,
 		Version: version,
-
-		PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
-			return initLightstep(lightstep)
-		},
 	}
 
-	root.PersistentFlags().StringVar(&lightstep, "lightstep", "", "Lightstep tracing endpoint (service:token@host:port)")
-
 	root.AddCommand(newCodeCmd(app))
 	root.AddCommand(newCreateCmd(app))
 	root.AddCommand(newDeleteCmd(app))
@@ -43,51 +28,3 @@ token to access the GitHub API with.`,
 
 	return root
 }
-
-// initLightstep parses the --lightstep=service:token@host:port flag and
-// enables tracing if non-empty.
-func initLightstep(config string) error {
-	if config == "" {
-		return nil
-	}
-
-	cut := func(s, sep string) (pre, post string) {
-		if i := strings.Index(s, sep); i >= 0 {
-			return s[:i], s[i+len(sep):]
-		}
-		return s, ""
-	}
-
-	// Parse service:token@host:port.
-	serviceToken, hostPort := cut(config, "@")
-	service, token := cut(serviceToken, ":")
-	host, port := cut(hostPort, ":")
-	portI, err := strconv.Atoi(port)
-	if err != nil {
-		return fmt.Errorf("invalid Lightstep configuration: %s", config)
-	}
-
-	opentracing.SetGlobalTracer(lightstep.NewTracer(lightstep.Options{
-		AccessToken: token,
-		Collector: lightstep.Endpoint{
-			Host:      host,
-			Port:      portI,
-			Plaintext: false,
-		},
-		Tags: opentracing.Tags{
-			lightstep.ComponentNameKey: service,
-		},
-	}))
-
-	// Report failure to record traces.
-	lightstep.SetGlobalEventHandler(func(ev lightstep.Event) {
-		switch ev := ev.(type) {
-		case lightstep.EventStatusReport, lightstep.MetricEventStatusReport:
-			// ignore
-		default:
-			log.Printf("[trace] %s", ev)
-		}
-	})
-
-	return nil
-}