revlog: ignore empty trailing chunks when reading segments When a merge commit creates an empty diff in the revlog, its offset may still be quite far from the end of the previous chunk. Skipping these empty chunks may reduce read size significantly. In most cases, there is no gain, and in some cases, little gain. On my clone of pypy, `hg manifest` reads 65% less bytes (96140 i/o 275943) for revision 4260 by ignoring the only empty trailing diff. For revision 2229, 35% (34557 i/o 53435) Sadly, this is difficult to reproduce, as hg clone can make its own different structure every time.

phase: isolate logic to update remote phrase through bundle2 pushkey Move the logic to build bundle2 pushkey part into its dedicated function. It will help to keep the logic clear when adding support for sending phases change using 'phase-heads' part.

phase: generate a push-race detection part on push We are about to switch phase pushing from using pushkey to using a the new dedicated binary part. We introduce the push race detection on its own to help detect potential impact.

phase: introduce a new 'check:phases' part This part checks if revisions are still in the same phase as when the bundle was generated. This is similar to what 'check:heads' or 'check:updated-heads' bundle2 part achieves for changesets. We needs seems before we can move away from pushkey usage from phase since pushkey has it own built-in push-race detection.

phase: gather remote phase information in a summary object We keep useful phase information around. The data will be reused with detecting push-race in later changesets.

phase: simplify the check for issue3781 shortcut in discovery We'll rework the code around this check. Limiting the entanglement will help with later changesets

exchange: fix issue3781 reference in the comment This comment is about: issue3781: Courtesy Phases synchronisation to publishing server prevent subrepo push Not about: issue3871: Slow hg log when template contains {file_adds}, {file_mods} and {file_dels}

phase: filter out non-draft item in "draft root" The on-disk file can contain draft root that are descendants of secret root. The resulting phase computation is correct, but the phases root content is not. I will send another series to introduce code that remove some of the cases where this can happens, but we first need to damage control the existing case. After this changeset, we can no longer advertise secret changeset as draft root.