configitems: add TODOs blocking the move out of experimental for revlogv2 These are the todos so far, we probably will have more, but we might as well list them while they're fresh in our minds. Differential Revision: https://phab.mercurial-scm.org/D10216

sidedata-exchange: rewrite sidedata on-the-fly whenever possible When a A exchanges with B, the difference of their supported sidedata categories is made, and the responsibility is always with the client to generated it: - If A pushes to B and B requires category `foo` that A does not have, A will need to generate it when sending it to B. - If A pulls from B and A needs category `foo`, it will generate `foo` before the end of the transaction. - Any category that is not required is removed. If peers are not compatible, abort. It is forbidden to rewrite sidedata for a rev that already has sidedata, since that would introduce unreachable (garbage) data in the data file, something we're not prepared for yet. Differential Revision: https://phab.mercurial-scm.org/D10032

revlog-index: add `replace_sidedata_info` method During a `pull` operation where the server does not provide sidedata, the client that requires it should generate them on-the-fly. In the generic case, we need to wait for the changelog + manifests + filelogs to be added, since we don't know what the sidedata computers might need: this means rewriting the sidedata of index entries from within the pull transaction (and no further back) right after we've added them. Both Python and C implementations only allow for rewriting the sidedata offset and length for revs within the transaction where they were created. Differential Revision: https://phab.mercurial-scm.org/D10031

revlogv2: temporarily forbid inline revlogs See inline comments. I plan to fix the underlying issue before revlogv2 is stabilized. Differential Revision: https://phab.mercurial-scm.org/D10030

changegroupv4: add sidedata helpers These helpers carry the information and computers needed to rewrite sidedata when generating/applying patches. We will be making use of them soon. Differential Revision: https://phab.mercurial-scm.org/D10029

revlog: add attribute on revlogs that specifies its kind The sidedata logic needs to check whether the revlog it's working on is a changelog, a manifest or a filelog. Furthermore, future versions of the revlog format will most likely see a split between the three types (i.e. they will store different information), so having this will be useful for other future endeavors as well. Differential Revision: https://phab.mercurial-scm.org/D10151