OSX: Trust the file watcher. owncloud#2297

* Use a bigger default force sync interval (2h)
* Allow the file watcher to schedule a sync while a sync for
  the same file is running.

src/gui/folderman.cpp

@@ -444,16 +444,19 @@ void FolderMan::slotScheduleSync( const QString& alias )
         return;
     }
 
+#ifndef Q_OS_MAC
     // The folder watcher fires a lot of bogus notifications during
     // a sync operation, both for actual user files and the database
     // and log. Never enqueue a folder for sync while it is syncing.
     // We lose some genuine sync requests that way, but that can't be
     // helped.
-    // ^^ FIXME: Note that this is not the case on OS X
+    // This works fine on OSX, where the folder watcher does not
+    // report changes done by our own process.
     if( _currentSyncFolder == alias ) {
         qDebug() << "folder " << alias << " is currently syncing. NOT scheduling.";
         return;
     }
+#endif
 
     if( _socketApi ) {
         // We want the SocketAPI to already now update so that it can show the EVAL icon

src/libsync/mirallconfigfile.cpp

@@ -365,7 +365,14 @@ quint64 MirallConfigFile::forceSyncInterval(const QString& connection) const
     QSettings settings(configFile(), QSettings::IniFormat);
     settings.beginGroup( con );
 
-    quint64 interval = settings.value( QLatin1String(forceSyncIntervalC), 10 * pollInterval ).toULongLong();
+    quint64 defaultInterval = 10 * pollInterval;
+#ifdef Q_OS_MAC
+    // On OSX we trust the file watcher. It does not report changes done
+    // by our own process and thus it's enabled during a folder's sync run.
+    // That means we don't need to do a full local discovery often.
+    defaultInterval = qMax(2 * 60 * 60 * 1000ull, defaultInterval); // >=2 hours
+#endif
+    quint64 interval = settings.value( QLatin1String(forceSyncIntervalC), defaultInterval ).toULongLong();
     if( interval < pollInterval) {
         qDebug() << "Force sync interval is less than the remote poll inteval, reverting to" << pollInterval;
         interval = pollInterval;