changelogv2: use a dedicated version number If we want to change the format, we need a new version number. We start with that. Differential Revision: https://phab.mercurial-scm.org/D10663

changelogv2: `copies-side-data` now implies `changelogv2` To store information about file changes and copies only requires sidedata support for the changelog. So we only enables `changelogv2`. This is less impactful and should help us to ship the changeset centric copy tracing sooner. Differential Revision: https://phab.mercurial-scm.org/D10662

changelogv2: allow upgrade from and to this format Differential Revision: https://phab.mercurial-scm.org/D10661

changelogv2: introduce a "changelogv2" feature Right now, this means using revlogv2, but only for the changelog. We will have the format more unique in future changesets. Differential Revision: https://phab.mercurial-scm.org/D10660

revlogv2: drop the code related to inlined revlogv2 Tevlogv2 will not use inlined revlog. As a result we can drop the associated code. Differential Revision: https://phab.mercurial-scm.org/D10659

revlogv2: no longer attempt to use inline for new revlog revlogv2 steered away for the inline feature. Differential Revision: https://phab.mercurial-scm.org/D10658

sidedata: use the "feature" to detect that sidedata are enabled This is more versatile than relying on the revlogv2 requirements. Differential Revision: https://phab.mercurial-scm.org/D10657

revlog: compress sidedata when doing "post-pull" sidedata update All path writing sidedata are now using compression (when appropriate). Differential Revision: https://phab.mercurial-scm.org/D10656

revlog: compress sidedata in `_writeentry` When appropriate we store the sidedata in a compressed form. Differential Revision: https://phab.mercurial-scm.org/D10655

revlog: apply compression mode while reading sidedata Right now, we only store things as PLAIN, but we are ready for some compression now. Future changeset will start using some. Differential Revision: https://phab.mercurial-scm.org/D10654

revlog: introduce a compression mode for sidedata in the revlog index We will use this for compression for the sidedata payload. Differential Revision: https://phab.mercurial-scm.org/D10653

revlog: implement a "default compression" mode The revlog docker is now storing a default compression engine. When a chunk use that compression, a dedicated mode is used in the revlog entry and we can directly route it to the right decompressor. We should probably make PLAIN and DEFAULT mode the only available mode for revlogv2, but this is something for later. Differential Revision: https://phab.mercurial-scm.org/D10652

revlog: add a `_get_decompressor` method This logic is non-trivial and we will need to reuse it. Differential Revision: https://phab.mercurial-scm.org/D10651

revlog: introduce a plain compression mode That mode is simple it means the chunk contains uncompressed data and can be used directly. Differential Revision: https://phab.mercurial-scm.org/D10650

revlog: use an intermediate variable for `data` in `_chunk` This will help us to dispatch this to the right decompressor. Differential Revision: https://phab.mercurial-scm.org/D10649