You can find a git repository for all versions up to 12.2 (created using `import-dscs` as suggested by pabs, plus a few refinements) at
https://salsa.debian.org/gioele/base-filesFeel free to fork and then reparent using "Settings" → "General" → "Remove fork relationship".
Kind regards, -- Gioele Barabucci <gio...@svario.it>