@Skif-off the library is to hold stuff that is to be shared between several plugins but is not needed by Geany itself.
What @codebrainz meant is that before that library the only way to share stuff was to put it in Geany itself even if Geany didn't use it.
Unfortunately since `glspi_selfile()` depends on a new version of Geany with `utils_tidy_path()` exported, adding `glspi_selfile()` to the library would mean the library and all plugins that used the library (not many so far) would depend on the Geany version. But I am not sure that the library checks the Geany version anyway.
So in general its probably not a good idea to add it to the library until thats fixed.