Switching backends

[Sebastian Tennant <sebyte@smolny.plus.com>]

Belated happy International Worker's Day,

I'd like to switch backends and migrate all my old nnfolder mail to
nnml (for ease of indexing).

Switching backends isn't a problem, but how to perform the migration
of already 'processed' mail?

As nnfolder uses mbox format, I considered copying the nnfolder mbox
file back to the spool file (/var/mail/sebyte) to effectively respool
all my mail using the new nnml select method, but there's an issue
over nnfolder-added headers, and this being gnus I've no doubt there's
a much cleaner (and easier) way to go about this.

Any help much appreciated.

Sebastian