deltas: at a `target_rev` parameter to finddeltainfo Otherwise, recomputing a delta for a revision might result in a delta against a later revision or a full snapshot thinking we are appending a new revision. We will make use of this during censoring (and later, stripping). Differential Revision: https://phab.mercurial-scm.org/D10887

revlog: list older-but-still-around file in `files` These older files will eventually be removed, but we have to take them in account until they are. So we update `files` to keep fncache happy. Differential Revision: https://phab.mercurial-scm.org/D10868

revlog: add docket method to request new content files If we want to write content into new files, we need to be able to ask for them. Differential Revision: https://phab.mercurial-scm.org/D10867

revlog: add a way to keep track of older uids in the docket When the revlog content is rewritten, we will use new files, to avoid truncating the previous ones. We need some way to keep track of the older files before we clean them up. Differential Revision: https://phab.mercurial-scm.org/D10866

revlog: factor the logic to determine the delta compression out This make the logic clearly isolated and documented and it will help use to reuse it during censors/strip. Differential Revision: https://phab.mercurial-scm.org/D10889

nodemap: fix some comment formatting Black seems unhappy about it. Differential Revision: https://phab.mercurial-scm.org/D10865

revlogv2: fix `hg verify` with revlog v2 We added a bunch of new files but we never teached some internal about it. This is now fixed. Differential Revision: https://phab.mercurial-scm.org/D10858