test-copies: test that copies' sidedata does not get corrupted during pull This is an important usecase. Differential Revision: https://phab.mercurial-scm.org/D10347

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