[OSM-dev] 412 Precondition failed and how to recover from it

[Dermot McNally]

The background:

A long and messy edit session involving complex and messy data. I
thought I managed to clean it up fairly well, but this may prove not
to be the case. Anyway, on uploading, I get the dreaded 412 error.

The editing is taking place in JOSM (latest, with layers), and I don't
think Potlatch was in use in the surrounding area. While it's not
virgin territory, all that was there was unwayed segments. Some I may
have deleted before the upload, but I can't be sure about this.

I do have a .osm file of my edits, and as I say, the map area where
this needs to go can easily be cleaned up if that's the cost of
getting the new stuff into place. My understanding of the message is
that the data in my .osm file is assuming something about the data on
server that proves not to be true. I'm happy to prune the offending
piece away in order to get the rest live, but can anyone offer tips as
to how I can work out which piece that might be? I suppose I could
just keep taking half my upload set until I find it, but that could
take a while...