Switch the default output format from Shapefile to GeoPackage

[jachym]

Hi. I'm attaching patch, which changes the default output vector format from ESRI Shapefile to OGC GeoPackage.

I've come trough most of the tools, but I expect, there are more. If you point me to missing code parts, I'll try to change them too.

Thank you for your help

[Even Rouault]

There's some intersection with ​https://trac.osgeo.org/gdal/wiki/rfc70_output_format_guess , which basically removes (or reduce it to a minimum proportion) any need for a default output format.

With your change, "ogr2ogr out.shp in.geojson" will generate a GeoPackage file called out.shp, which is unexpected, and violates a GeoPackage requirement that requires the .gpkg extension. And this would be quite a disruptive change for a lot of existing scripts.

With RFC70 (unimplemented yet), "ogr2ogr out.shp in.geojson" would generate a shapefile, and "ogr2ogr out.gpkg in.geojson" a GeoPackage. "ogr2ogr out in_with_several_layers.gml" would continue to create a 'out' directory with a shapefile per input layer in it.

[jachym]

Hi Even,

whatever you think is the best.

I agree, having "guessing" mechanism of output file type would probably be the best option

P.S. Just asking: is there any reason, why GDAL interprets directory with shapefiles as data source with layers, but this does not apply on directory with geopackages?

[Jukka Rahkonen]

About your question, initial reason is probably historical and I guess that it has been made so to help conversion to/from formats which support multiple layers. Unlike shapefiles geopackage can have however many layers so there is no such need. In addition I guess it could be complicated to handle the situation because either you need to open an own connection for each gpkg in the directory or to use one gpkg as a master and attach the other geopackages into that. I believe that it would get complicated to add new layers into such bunch-of-packages.

[Even Rouault]

In 40774:

RFC 70: Guess output format from extension of output filename, if no explicit format passed to C++ or Python utilities (also fixes #7112)