Reliable identity & version in the MBTiles

[klokan]

For TileServer GL as well as for the mobile app - it would make sense to have in the SQLite/MBTiles in metadata table an reliable identifier telling these vector tiles are from OSM2VectorTiles project of a given version.

This is something what we should guarantee to provide in all future MBTiles from now on.

Then any client can validate if they support the MBTiles and if they have the appropriate set of styles and assets to display that particular version.

In the original V1 tiles we have:

sqlite> select * from metadata;
id|osm2vectortiles
name|osm2vectortiles
version|1
description|Extract from osm2vectortiles.org
attribution|© OpenStreetMap contributors
format|pbf

In the latest V2 tiles there is:

sqlite> select * from metadata;
id|osm2vectortiles
name|osm2vectortiles
version|2.0
format|pbf
description|Extract from http://osm2vectortiles.org
attribution|<a href="http://www.openstreetmap.org/about/" target="_blank">&copy; OpenStreetMap contributors</a>
mtime|1463000297761

So the name and version are already used in an expected way.
The version use more or less complies to the TileJSON spec: https://github.com/mapbox/tilejson-spec/tree/master/2.1.0
(major versions upgrade means the styles are not anymore compatible).

Unfortunately, the version has not been updated with the releases recently - latest release is v2.3, but version in tiles remains to be "2.0"

The actions on this ticket:

• Ensure (and remember) that we in future should always keep the "name" as "osm2vectortiles" or this string should be at least included and could be tested by clients with a case-insensitive filter.
• Implement an automated process which updates the version appropriately - ideally by getting the latest tag release from git with a command like git describe --abbrev=0 --tags with stripped first character. Of course, we have to first make a release of the code on github and then use the code to generate the new vector tiles - if this should run well.