From Bradley Anderegg, "The first change just exposes the archive extension list so that

external applications can determine if an archive extension is valid.

The second change is a bug fix in Registry::read(const ReadFunctor&)
where if you pass in valid options they get wiped out after the archive
is loaded but before being passed along to the plugin."

src/osgDB/Registry.cpp

@@ -1036,7 +1036,12 @@ ReaderWriter::ReadResult Registry::read(const ReadFunctor& readFunctor)
 
             osgDB::Archive* archive = result.getArchive();
         
-            osg::ref_ptr<Options> options = new Options;
+            //if valid options were passed through the read functor clone them
+            //otherwise make new options
+            osg::ref_ptr<osgDB::ReaderWriter::Options> options = readFunctor._options ?
+                readFunctor._options->cloneOptions() :
+                new osgDB::ReaderWriter::Options;
+
             options->setDatabasePath(archiveName);
 
             return archive->readObject(fileName,options.get());