Add easier headless configuration.

This will allow setting up a remote with copy&paste of values to a headless machine. It will allow copy+pasting a token into the configuration.

This requires rclone to be on a machine with a proper browser. Custom client id and secrets are supported.

To test token generation, use `rclone auth "fs type"`.

fs/config.go

@@ -532,3 +532,47 @@ func EditConfig() {
 		}
 	}
 }
+
+// Duplicated from oauthutil to avoid circular reference.
+const (
+	// ConfigClientID is the config key used to store the client id
+	ConfigClientID = "client_id"
+
+	// ConfigClientSecret is the config key used to store the client secret
+	ConfigClientSecret = "client_secret"
+
+	// ConfigAutomatic indicates that we want non-interactive configuration
+	ConfigAutomatic = "config_automatic"
+)
+
+// Authorize is for remote authorization of headless machines.
+func Authorize() {
+	args := pflag.Args()[1:]
+	switch len(args) {
+	case 1, 3:
+	default:
+		log.Fatalf("Invalid number of arguments: %d", len(args))
+	}
+	newType := args[0]
+	fs, err := Find(newType)
+	if err != nil {
+		log.Fatalf("Failed to find fs: %v", err)
+	}
+
+	if fs.Config == nil {
+		log.Fatalf("No configuration on fs %v", newType)
+	}
+	// Name used for temporary fs
+	name := "**temp-fs**"
+
+	// Make sure we delete it
+	defer DeleteRemote(name)
+
+	// Indicate that we want fully automatic configuration.
+	ConfigFile.SetValue(name, ConfigAutomatic, "yes")
+	if len(args) == 3 {
+		ConfigFile.SetValue(name, ConfigClientID, args[1])
+		ConfigFile.SetValue(name, ConfigClientSecret, args[2])
+	}
+	fs.Config(name)
+}