[gocritic]: Improve code quality.

processStanzas.go

@@ -190,6 +190,28 @@ func processStanzas(client *xmpp.Client, muc string, mucNick string, feeds []str
 						log.Fatal("Error: Failed sending message to ", v.Remote, ": ", err)
 					}
 				}
+			default:
+				reply := `Unknown command, type "help" for a list of supported commands.`
+				if v.Type == "groupchat" {
+					_, err = client.Send(xmpp.Chat{
+						Remote: muc,
+						Type:   "groupchat", Text: strings.Split(v.Remote, "/")[1] + ": " + reply,
+					})
+					if err != nil {
+						log.Fatal("Error: Failed sending message to MUC:", err)
+					}
+				} else if v.Type == "chat" {
+					_, err = client.Send(xmpp.Chat{
+						Remote: v.Remote,
+						Type:   "chat", Text: reply,
+					})
+					if err != nil {
+						log.Fatal("Error: Failed sending message to ", v.Remote, ": ", err)
+					}
+				}
+
+			// Reply with repo address for `source`.
+			case "source":
 			}
 
 		// Reply to pings and disco queries.