wipe "known categories" cache when database transients are reset

closes #1626
closes #1632

app/src/main/java/org/fdroid/fdroid/data/AppProvider.java

@@ -983,6 +983,7 @@ public class AppProvider extends FDroidProvider {
                 categoryValues.put(CatJoinTable.Cols.CATEGORY_ID, categoryId);
                 db().insert(getCatJoinTableName(), null, categoryValues);
             }
+            getContext().getContentResolver().notifyChange(CategoryProvider.getContentUri(), null);
         }
     }
 

app/src/main/java/org/fdroid/fdroid/data/CategoryProvider.java

@@ -17,6 +17,7 @@ import java.util.Locale;
 import java.util.Map;
 
 public class CategoryProvider extends FDroidProvider {
+    public static final String TAG = "CategoryProvider";
 
     public static final class Helper {
         private Helper() {
@@ -26,7 +27,7 @@ public class CategoryProvider extends FDroidProvider {
          * During repo updates, each app needs to know the ID of each category it belongs to.
          * This results in lots of database lookups, usually at least one for each app, sometimes more.
          * To improve performance, this caches the association between categories and their database IDs.
-         *
+         * <p>
          * It can stay around for the entire F-Droid process, even across multiple repo updates, as we
          * don't actually remove data from the categories table.
          */

app/src/main/java/org/fdroid/fdroid/data/DBHelper.java

@@ -1318,6 +1318,7 @@ public class DBHelper extends SQLiteOpenHelper {
         Utils.debugLog(TAG, "Removing all index tables, they will be recreated next time F-Droid updates.");
 
         Preferences.get().resetLastUpdateCheck();
+        CategoryProvider.Helper.clearCategoryIdCache();
 
         db.beginTransaction();
         try {