reimplemented export process

app/common/filefunctions.h

@@ -67,6 +67,23 @@ public:
 
   static QString ReadFileAsString(const QString& filename);
 
+  /**
+   * @brief Returns a temporary filename that can be used while writing rather than the original
+   *
+   * If overwriting a file, it's safest to write to a new file first and then only replace it at
+   * the end so that if the program crashes or the user cancels the save half way through, the
+   * original file is still intact.
+   *
+   * This function returns a slight variant of the filename provided that's guaranteed to not exist
+   * and therefore won't overwrite anything important.
+   */
+  static QString GetSafeTemporaryFilename(const QString& original);
+
+  /**
+   * @brief Renames a file from `from` to `to`, deleting `to` if such a file already exists first
+   */
+  static bool RenameFileAllowOverwrite(const QString& from, const QString& to);
+
 };