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

sidedata-exchange: add `wanted_sidedata` and `sidedata_computers` to repos Each repo will advertise the sidedata categories it requires (categories being unique and canonical), and have a set of "computers", functions to generate sidedata from `(repo, revlog, rev, previous_sidedata)`, for a given category. The set of computers can be a superset of the set of the wanted categories, but not smaller: repos are expected to be coherent in their handling of sidedata. Differential Revision: https://phab.mercurial-scm.org/D10028

delta: add sidedata field to revision delta When emitting revision delta, we need to also emit the sidedata information just added in the revlogv2 format if appropriate. Differential Revision: https://phab.mercurial-scm.org/D10027

changegroup: add v4 changegroup for revlog v2 exchange This change only adds the required infrastructure for the new changegroup format and does not do any actual exchange. This will be done in the next patches. Differential Revision: https://phab.mercurial-scm.org/D10026