A file loader should be used only for one load operation, including errors handling. If an error occurs, you can reconfigure the loader
and relaunch the operation with [[email protected]_async].
Running a `GtkSourceFileLoader` is an undoable action for the [class@Buffer].
After a file loading, the buffer is reset to the contents provided by the [[email protected]] or [[email protected]], so the buffer is
set as “unmodified”, that is, [[email protected]_modified] is called with false. If the
contents isn't saved somewhere (for example if you load from stdin), then you should probably call [[email protected]_modified]
with true after calling [[email protected]_finish].