The actual change to the API is pretty simple. First, the 'sessionkey' parameter has been superseded by 'filekey', though 'sessionkey' remains
for
compatibility.
Seems to me like this doesn't need any client-visible changes; any objection to just leaving it labeled as is? It's a key to an 'upload session', so I wouldn't assume it has any specific relationship to HTTP session cookies...
Neilk and I talked about that, but it seemed misleading. While it could be argued that the UploadWizard implements the concept of an upload session, it doesn't really carry through to the API. Each key is linked to a specific file, whereas I'd expect an upload session to be an abstraction that could contain multiple files. Previously, sessionkey was really referring to the file key that was stored in the session.
We decided that changing it made sense since it was possible to deprecate the old name without removing it, which gave us both clarity and functionality. Had that been impossible, leaving it unchanged was the next-best option.
-Ian