LibCore: Add account add_extra_gid and remove_extra_gid

Author: bplaat

Userland/Libraries/LibCore/Account.h

@@ -54,6 +54,13 @@ class Account {
     void set_gecos(StringView gecos) { m_gecos = gecos; }
     void set_deleted() { m_deleted = true; }
     void set_extra_gids(Vector<gid_t> extra_gids) { m_extra_gids = move(extra_gids); }
+    void add_extra_gid(gid_t gid) { m_extra_gids.append(gid); }
+
+    void remove_extra_gid(gid_t gid)
+    {
+        m_extra_gids.remove_all_matching([gid](auto g) { return g == gid; });
+    }
+
     void delete_password();
 
     // A nonexistent password means that this account was missing from /etc/shadow.

Userland/Utilities/usermod.cpp

@@ -188,19 +188,12 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     }
 
     if (append_extra_gids) {
-        for (auto gid : target_account.extra_gids())
-            extra_gids.append(gid);
-    }
-
-    if (remove_extra_gids) {
-        Vector<gid_t> current_extra_gids = target_account.extra_gids();
         for (auto gid : extra_gids)
-            current_extra_gids.remove_all_matching([gid](auto current_gid) { return current_gid == gid; });
-
-        extra_gids = move(current_extra_gids);
-    }
-
-    if (!extra_gids.is_empty() || remove_extra_gids) {
+            target_account.add_extra_gid(gid);
+    } else if (remove_extra_gids) {
+        for (auto gid : extra_gids)
+            target_account.remove_extra_gid(gid);
+    } else {
         target_account.set_extra_gids(extra_gids);
     }