test-copies: simplify some conditional output Now that all computation using sidedata give the same result, we can simplify conditional Differential Revision: https://phab.mercurial-scm.org/D10346

sidedata: move documentation about sidedata helpers to sidedata module Differential Revision: https://phab.mercurial-scm.org/D10361

sidedata: move sidedata-related utils to the dedicated module Differential Revision: https://phab.mercurial-scm.org/D10360

sidedata: replace sidedata upgrade mechanism with the new one Note: this is split into a separate change (like some other patches in this series) because it's not easy to have all patches work 100% and this seemed easier for reviewers. When cloning or upgrading a repo, we may need to compute (or remove) sidedata. This is the same mechanism that is used in exchange, so we re-use the new system to simplify the code and fix the remaining issues (correctly dropping flags and handling partial removal, etc.). This also highlighted an issue with `test-copies-in-changeset.t` that kept sidedata categories that are not relevant anymore. They should probably be dropped entirely, but that would be for another patch. Differential Revision: https://phab.mercurial-scm.org/D10359

sidedata: add a way of replacing an existing sidedata computer This will be useful in a future patch to replace a sequential computer with a parallel computer. We only allow for explicit replacement, to force the users to think about overriding computers. Differential Revision: https://phab.mercurial-scm.org/D10358

bundle2: remove restriction around sidedata We are now capable of generating the missing sidedata on-the-fly. Differential Revision: https://phab.mercurial-scm.org/D10345

sidedata: enable sidedata computers to optionally rewrite flags Sidedata computers may want to influence the flags of the revision they touch. For example, the computer for changelog-based copytracing can add a flag to signify that this revision might affect copytracing, inversely removing said flag if the information is no longer applicable. See inline documentation in `storageutil` for more details. Differential Revision: https://phab.mercurial-scm.org/D10344

cg4: introduce protocol flag to signify the presence of sidedata We need a way of signaling whether the current revision has sidedata or not, and re-using the revision flags would waste potential revlog flags and mix two normally independent layers. In this change, we add a single byte at the start of the ch4 delta header to set potential protocol flags. We also reclaim the revlog flag for sidedata, since it is no longer used, in its place now lives the (also experimental) copytracing flag. When generating deltas, apply the `CG_FLAG_SIDEDATA` flag if there is sidedata. When applying the deltas, if said flag is present, the next chunk contains the sidedata. Differential Revision: https://phab.mercurial-scm.org/D10343

changegroup: don't limit cgv4 to revlogv2 repos To help the transition from revlogv1 to revlogv2, we need to be able to enable cgv4 for revlogv1 repos, so that revlogv2 clients can handle adding/removing sidedata over the wire. Differential Revision: https://phab.mercurial-scm.org/D10342

sidedata: gate sidedata functionality to revlogv2 in more places Since revlogv1 is not capable of storing sidedata, we prevent sidedata mechanisms around the revlog layer from doing anything. We however keep the ones that allow a revlogv1 repo to generate sidedata on-the-fly on a push, the pull case simply does not add the sidedata to the revlog. Differential Revision: https://phab.mercurial-scm.org/D10341