Maybe:
```
/* \brief Change the base path of a URL: fromPath/fromFile -> toPath/toFile
  Handles changes in path separator and filename URL encoding if necessary to derive toFile.
  \param fromPath the base path of the original URL
  \param fromFile the filename portion of the original URL
  \param toPath the base path of the resulting URL
  \return the full path.
 */
std::string ChangeBasePath(const std::string &fromPath, const std::string &fromFile, const std::string &toPath)
```