Directory monitoring tracks invalid ZIM files too

A ZIM file that failed to be added to the library isn't just
discarded by directory monitoring but is added to the set of known
ZIM files with a proper status. This enables to process updates to
such files more efficiently (coming next).

src/contentmanager.cpp

@@ -945,16 +945,19 @@ bool ContentManager::handleZimFileInMonitoredDirLogged(QString dir, QString file
 int ContentManager::handleZimFileInMonitoredDir(QString dir, QString fileName)
 {
     const auto bookPath = QDir::toNativeSeparators(dir + "/" + fileName);
-    kiwix::Manager manager(mp_library->getKiwixLibrary());
 
     if ( mp_library->isBeingDownloadedByUs(bookPath) ) {
         return MonitoredZimFileInfo::BEING_DOWNLOADED_BY_US;
-    } else if ( manager.addBookFromPath(bookPath.toStdString()) ) {
-        m_knownZimsInDir[dir].insert(fileName, MonitoredZimFileInfo());
-        return MonitoredZimFileInfo::ADDED_TO_THE_LIBRARY;
-    } else {
-        return MonitoredZimFileInfo::COULD_NOT_BE_ADDED_TO_THE_LIBRARY;
     }
+
+    MonitoredZimFileInfo zfi;
+    kiwix::Manager manager(mp_library->getKiwixLibrary());
+    const bool addedToLib = manager.addBookFromPath(bookPath.toStdString());
+    zfi.status = addedToLib
+               ? MonitoredZimFileInfo::ADDED_TO_THE_LIBRARY
+               : MonitoredZimFileInfo::COULD_NOT_BE_ADDED_TO_THE_LIBRARY;
+    m_knownZimsInDir[dir].insert(fileName, zfi);
+    return zfi.status;
 }
 
 ContentManager::QStringSet ContentManager::getLibraryZims(QString dirPath) const

src/contentmanager.h

@@ -113,6 +113,9 @@ private: // types
     {
         enum ZimFileStatus
         {
+            // try to add this file to the library right away
+            NO_INFO,
+
             // the file is known to be downloaded by our own download manager
             BEING_DOWNLOADED_BY_US,
 
@@ -123,7 +126,7 @@ private: // types
             COULD_NOT_BE_ADDED_TO_THE_LIBRARY
         };
 
-        ZimFileStatus status = ADDED_TO_THE_LIBRARY;
+        ZimFileStatus status = NO_INFO;
     };
 
     typedef QMap<QString, MonitoredZimFileInfo> ZimFileName2InfoMap;