List deletions

[mitra42]

Lists should support deletion, note that a deletion is just a flag of some sort (I think YJS supports it) so any retrieval should also have the option of eliminating deletions or retaining them.

Note there is already code that filters out duplicates, it probably belongs as a argument to that code to decide whether to eliminate Deletions (first - so deduplications get the not-deleted one).

[mitra42]

Note - part of this is having some way to delete a list all the way back to empty.

[mitra42]

Moved to internetarchive/dweb-transports#11