This one came up yesterday, while preparing for @organicmaps GSoC student work.
When developing an editor, you need to work with OSM Sandbox, a dev copy of API with no data. Sometimes it's frustrating because complex data is where an editor breaks. Usually I downloaded an OSM extract in JOSM, fixed ids, and uploaded it to the Sandbox, but on the 100th time I gave up.
https://github.com/Zverik/osm_to_sandbox
This script helps you transfer a bbox worth of data in two commands, one of which is pip install.
@zverik Does the script also change IDs? What does "fix ids" mean? For readers' info, Organic Maps Editor doesn't store IDs and doesn't rely on them.