largefiles: wrap "rebase.rebase" for functions using it directly Before this patch, largefiles extension wraps only "rebase" in the command table by "extensions.wrapcommand". But there are some functions using "rebase.rebase" directly. Without special care for them, largefiles extension can't work correctly with such functions. In addition to it, "special care" often becomes complicated and awkward. For example: - "unshelve" can't get correct result of "rebase.rebase", because of lack of special care - special care for "hg pull --rebase" causes issue3861 This patch wraps "rebase.rebase" for functions using it directly. For simplicity, this patch keeps 'special care for "hg pull --rebase"'. It is removed in the subsequent patch.

changegroup: introduce cg2packer/unpacker cg2 supports generaldelta in changegroups, to be used in bundle2. Since generaldelta is handled directly in cg2, reordering is switched off by default.

push: send highest changegroup format supported by both side When using bundle2, we find the common subset of supported changegroup-packers and we pick the max of them. This allow to use generaldelta aware changegroups through bundle2.

getbundle: send highest changegroup format supported by both side When using bundle2, we find the common subset of supported changegroup-packers and we pick the max of them. This allow to use generaldelta aware changegroup through bundle2.

changegroup: allow use of different cg#packer in getchangegroupraw This will allow the use of general delta aware changegroup formats.

changegroup: introduce "raw" versions of some commands The commands getchangegroup, getlocalchangegroup and getsubset now each have a version ending in -raw. The raw versions return the chunk generator from the changegroup packer directly, without wrapping it in a chunkbuffer and unpacker. This avoids extra chunkbuffers in the bundle2 code path. Also, the raw versions can be extended to support alternative packers in the future, to be used from bundle2.