changegroup: pass function to build delta header into constructor...
changegroup: pass function to build delta header into constructor
Previously, the delta header struct format was defined on each
class and each class had a separate function for building the
delta header.
We replace both of these with an argument to __init__ containing
a callable that can format a delta header given a revisiondelta
instance.
Differential Revision:
https://phab.mercurial-scm.org/D4079
