Update usage message

README.md

@@ -40,12 +40,12 @@ as they lack an official package manager.
 Usage
 -----
 
-    river [-cert path] [-key path] [-port port] path
+    river [-cert file] [-key file] [-port port] directory
 
-River serves the music located at the given path. The music can be accessed via
-a client on the port specified with the -port flag, or the default port. If the
--cert and -key flags are specified, River will listen for HTTPS connections;
-otherwise, River will listen for HTTP connections.
+river serves the music in the given directory. The music can be accessed via a
+client on port 21313, or on the port named by the -port flag. If the -cert and
+-key flags are specified, river will listen for HTTPS connections; otherwise,
+river will listen for HTTP connections.
 
 [river-web](https://github.com/wwalexander/river-web) is a browser-based River
 client.

river.go

@@ -624,12 +624,12 @@ func getHash() (hash []byte, err error) {
 	return
 }
 
-const usage = `usage of river: river [-cert path] [-key path] [-port port] path
+const usage = `usage: river [-cert file] [-key file] [-port port] directory
 
-River serves the music located at the named path. The music can be accessed via
-a client on port 21313, or on the port named by the -port flag. If the -cert and
--key flags are specified, River will listen for HTTPS connections; otherwise,
-River will listen for HTTP connections.`
+river serves the music in the given directory. The music can be accessed via a
+client on port 21313, or on the port named by the -port flag. If the -cert and
+-key flags are specified, river will listen for HTTPS connections; otherwise,
+river will listen for HTTP connections.`
 
 func main() {
 	fcert := flag.String(fcertName, "", "the TLS certificate to use")