changegroup: declare shallow flag in constructor
Thus begins the process of better formalizing ellipses and shallow
changegroup generation mode so it is tracked by cgpacker at
construction time instead of bolted on after the fact by a
wrapper function.
Differential Revision: https://phab.mercurial-scm.org/D4086
changegroup: make some packer attributes private
These methods and attributes are low level and should not be
called or outside outside of instances. Indicate as such through
naming.
Differential Revision: https://phab.mercurial-scm.org/D4085
changegroup: rename cg1packer to cgpacker
There is now only a single class. We don't need to encode the
version in its name since the version is a lie.
Differential Revision: https://phab.mercurial-scm.org/D4084