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

sidedata: register copies sidedata computer regardless of the revlog version Repositories should not gate their sidedata computers based on any requirement, only their wanted sidedata. A repository might need to generate sidedata wanted by the peer that it itself does not want. Differential Revision: https://phab.mercurial-scm.org/D10340

revlog: replace the old `revlog_kind` approach with the new `target` one The new `target` attribute supersedes the previous one. Differential Revision: https://phab.mercurial-scm.org/D10353

revlog: introduce an explicit tracking of what the revlog is about Since the dawn of time, people have been forced to rely to lossy introspection of the index filename to determine what the purpose and role of the revlog they encounter is. This is hacky, error prone, inflexible, abstraction-leaky, <insert-your-own-complaints-here>. In f63299ee7e4d Raphaël introduced a new attribute to track this information: `revlog_kind`. However it is initialized in an odd place and various instances end up not having it set. In addition is only tracking some of the information we end up having to introspect in various pieces of code. So we add a new attribute that holds more data and is more strictly enforced. This work is done in collaboration with Raphaël. The `revlog_kind` one will be removed/adapted in the next changeset. We expect to be able to clean up various existing piece of code and to simplify coming work around the newer revlog format. Differential Revision: https://phab.mercurial-scm.org/D10352

config: add --source option to include source of value Showing the source of each config option is quite useful and not something the user should have to reach for the `--debug` flag for. I updates documentation and tests, except for one place in `test-hgrc.t` where I thought the test might have been intended to also test that `--debug` results in `ui.quiet` etc being test. Differential Revision: https://phab.mercurial-scm.org/D10668

rewriteutil: say how many commits would become orphan if commit is rewritten This copies the message from the evolve extension, but modifies it a bit to work with the grammar (in particular with the use of "change branch of" as `action`). I don't know why it doesn't use the same `_formatrevs()` as for public commmits. Differential Revision: https://phab.mercurial-scm.org/D10671

rewriteutil: give examples of public changesets that can't be rewritten This patch copies the feature from the evolve extension. Differential Revision: https://phab.mercurial-scm.org/D10670

convert: update p4 for Python 3 Differential Revision: https://phab.mercurial-scm.org/D10703