Single changeset query

[Zverik]

OWL database can produce diff for a single changeset, that is, a json of all changes in a changeset. This is obviously a valuable function, so I propose to add a /changeset/:id.format API call. This pull request adds it.

Warning: code untested. Though the change is quite simple.

[ppawel]

Sorry for no response for a long time. I just got back to working on OWL. Unfortunately, there are major changes again in the database and your commit is not auto mergable. I will merge it manually.

Thank you for the code, soon OWL should be finally stable enough so that people can start contributing :)

[Zverik]

Pavel, nice to hear from you! The thing is, you have already set up a database of all changes in OSM, and it can be used in many ways, apart from OWL site. It would be great to have as much API as possible. For example, I'd like to create a page that displays changes in a specific changeset, and it can already be done: your server has all the data. The problem is in API. So please, don't just concentrate on OWL part and wait for it to be perfect. Think of API and announce it separately, so other people could make different tools employing it.

(well, and thank you for this project, it can't be said too often :)

[ppawel]

I think you are 100% about defining the API - I'm maybe focused too much on the implementation part. Implementation can always be improved I guess. I have new version of the OWL backend almost ready to replace the current one, after that I will focus on the API and the new history tab project to use the API.