I'd like to merge shapefiles of different geometry types into a single geojson feature collection, but OGR says it doesn't support update of GeoJSON files:

$ ogr2ogr -f GeoJSON -t_srs crs:84 -lco GEOMETRY_AS_COLLECTION merge.geojson points.shp
$ ogr2ogr -f GeoJSON -t_srs crs:84 -update -append merge.geojson -lco GEOMETRY_AS_COLLECTION lines.shp -nln merged
ERROR 4: GeoJSON Driver doesn't support update.
FAILURE:
Unable to open existing output datasource `merge.geojson'.

This seems like a common use case to me. Am I missing something obvious in the ogr2ogr manual? I can put together something in python (and finally use fiona) but I'm rather surprised I don't see anything existing when searching here or github... which makes me thing I'm messing something up.

thanks!