Update README and reinstate custom usage.For

Gopkg.toml

@@ -11,10 +11,6 @@
   name = "github.com/oklog/run"
   version = "1.0.0"
 
-[[constraint]]
-  name = "github.com/peterbourgon/usage"
-  version = "1.0.0"
-
 [[constraint]]
   name = "github.com/pkg/errors"
   version = "0.8.0"

README.md

@@ -22,20 +22,20 @@ USAGE
   fastly-exporter [flags]
 
 FLAGS
-  -debug false                             log debug information
+  -debug false                             Log debug information
   -endpoint http://127.0.0.1:8080/metrics  Prometheus /metrics endpoint
-  -namespace ...                           Prometheus namespace
-  -service ...                             Fastly service ID (repeatable)
-  -subsystem ...                           Prometheus subsystem
-  -token ...                               Fastly API token
+  -namespace ...                           Prometheus namespace (optional)
+  -service ...                             Specific Fastly service ID (optional, repeatable)
+  -subsystem ...                           Prometheus subsystem (optional)
+  -token ...                               Fastly API token (required)
 
 VERSION
-  1.0.0
+  2.0.0
 ```
 
-A valid API -token and at least one -service ID are mandatory. Your service ID
-is available at the top of your [Fastly dashboard][db]. [See this link][token]
-for information on creating API tokens.
+A valid Fastly API -token is mandatory. [See this link][token] for information
+on creating API tokens. Providing individual -service IDs is optional, and will
+Service IDs are available at the top of your [Fastly dashboard][db]. 
 
-[db]: https://manage.fastly.com/services/all
 [token]: https://docs.fastly.com/guides/account-management-and-security/using-api-tokens#creating-api-tokens
+[db]: https://manage.fastly.com/services/all

main.go

@@ -9,12 +9,12 @@ import (
 	"os"
 	"os/signal"
 	"strings"
+	"text/tabwriter"
 	"time"
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
 	"github.com/oklog/run"
-	"github.com/peterbourgon/usage"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
@@ -31,7 +31,7 @@ func main() {
 		debug      = fs.Bool("debug", false, "Log debug information")
 	)
 	fs.Var(&serviceIDs, "service", "Specific Fastly service ID (optional, repeatable)")
-	fs.Usage = usage.For(fs, "fastly-exporter [flags]")
+	fs.Usage = usageFor(fs, "fastly-exporter [flags]")
 	fs.Parse(os.Args[1:])
 
 	var logger log.Logger
@@ -185,3 +185,25 @@ func (ss *stringslice) String() string {
 type httpClient interface {
 	Do(*http.Request) (*http.Response, error)
 }
+
+func usageFor(fs *flag.FlagSet, short string) func() {
+	return func() {
+		fmt.Fprintf(os.Stderr, "USAGE\n")
+		fmt.Fprintf(os.Stderr, "  %s\n", short)
+		fmt.Fprintf(os.Stderr, "\n")
+		fmt.Fprintf(os.Stderr, "FLAGS\n")
+		w := tabwriter.NewWriter(os.Stderr, 0, 2, 2, ' ', 0)
+		fs.VisitAll(func(f *flag.Flag) {
+			def := f.DefValue
+			if def == "" {
+				def = "..."
+			}
+			fmt.Fprintf(w, "\t-%s %s\t%s\n", f.Name, def, f.Usage)
+		})
+		w.Flush()
+		fmt.Fprintf(os.Stderr, "\n")
+		fmt.Fprintf(os.Stderr, "VERSION\n")
+		fmt.Fprintf(os.Stderr, "  %s\n", version)
+		fmt.Fprintf(os.Stderr, "\n")
+	}
+}