API: allow querying changesets by tag

[grischard]

The current API allows querying changesets by user and by time, and is limited to 100 changesets at a time.

Being able to search by tags, e.g. imagery_used=My bad imagery or created_by=Very buggy editor 1.0 would make a lot of QA tasks easier.

(Are there any tools that make this possible already?)

[tomhughes]

Tags aren't indexed at the moment so this isn't really possible without a schema change.

[zerebubuth]

I think this would be a really useful service to have and, like Nominatim or Taginfo, it could be run independently of the API. All the data can be downloaded and kept up-to-date using the changeset dumps and diffs.

Since both of those also include the discussions, then it would also be possible to find keywords mentioned in discussions, which might also be useful.

[willemarcel]

@grischard OSMCha offers what you need: https://osmcha.mapbox.com/