wireproto: start to associate frame generation with a stream
An upcoming commit will introduce "streams" into the frame-based wire
protocol. In preparation for this invasive change, we introduce a basic
"stream" class and have all operations that create frames also operate
alongside a stream instance.
Differential Revision: https://phab.mercurial-scm.org/D2906
https://bz.mercurial-scm.org/1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..