Write usage information

src/github.com/matrix-org/dendrite/tools/create-room-events/main.go

@@ -5,6 +5,7 @@ package main
 import (
 	"encoding/base64"
 	"encoding/json"
+	"flag"
 	"fmt"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/gomatrixserverlib"
@@ -14,22 +15,44 @@ import (
 	"time"
 )
 
+const usage = `Usage: %s
+
+Generate a list of matrix room events for load testing.
+Writes the events to stdout separated by new lines
+
+Environment:
+
+    SERVER_NAME     The name of the matrix server to generate events for.
+                    (default: "localhost")
+
+    KEY_ID          The ID of the key used to sign the events.
+                    (default: "ed25519:auto")
+
+    PRIVATE_KEY     Base64 encoded private key to sign events with
+                    (default: <base64 encoded key of 0>)
+
+    ROOM_ID         The room ID to generate events in.
+                    (default: "!roomid:$SERVER_NAME")
+
+    USER_ID         The user ID to use as the event sender.
+                    (default: "@userid:$SERVER_NAME")
+
+    MESSAGE_COUNT   The number of m.room.messsage events to generate.
+                    (default: 10)
+
+    FORMAT          The output format to use for the messages.
+                        INPUT -> api.InputRoomEvent
+                        RAW   -> gomatrixserverlib.Event
+                    (default: INPUT)
+`
+
 var (
-	// The name of the matrix server to generate events for.
 	serverName       = defaulting(os.Getenv("SERVER_NAME"), "localhost")
-	// The ID of the key used to sign the events.
 	keyID            = defaulting(os.Getenv("KEY_ID"), "ed25519:auto")
-	// Base64 encoded private key to sign the events with.
 	privateKeyString = defaulting(os.Getenv("PRIVATE_KEY"), defaultKey)
-	// The room ID to generate events in.
 	roomID           = defaulting(os.Getenv("ROOM_ID"), "!roomid:"+serverName)
-	// The user ID to use for as the event sender.
 	userID           = defaulting(os.Getenv("USER_ID"), "@userid:"+serverName)
-	// The number of m.room.messsage events to generate.
 	messageCount     = defaulting(os.Getenv("MESSAGE_COUNT"), "10")
-	// The output format to use for the messages.
-	//	INPUT -> api.InputRoomEvent
-	//  RAW   -> gomatrixserverlib.Event
 	format           = defaulting(os.Getenv("FORMAT"), "INPUT")
 )
 
@@ -50,6 +73,10 @@ var b gomatrixserverlib.EventBuilder
 var eventID int
 
 func main() {
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, usage, os.Args[0])
+	}
+	flag.Parse()
 	// Decode the ed25519 private key.
 	privateKeyBytes, err := base64.RawStdEncoding.DecodeString(privateKeyString)
 	if err != nil {