condensediffs has been updated to handle the migration of

LegacyFileDiffData entries to RawFileDiffData. A lot of work went into

optimizing this. These are converted in batches, with minimal SQL

queries on a modern database (read: not sqlite3).
A run of condensediffs on a copy of a real-world database containing

650,000 diffs (all stored in LegacyFileDiffData entries) took 15 minutes

to convert, with a space savings of 80% (3.6GB down to 714MB).

Ran this many, many times without problems.
This was tested on sqlite, MySQL, and PostgreSQL.