changegroup: clean up changelog callback...
changegroup: clean up changelog callback
changelog.read() calls changelog.changelogrevion() then turns it into
a tuple. Let's call changelogrevision() directly and used named
attributes to make code easier to read.
While we're here, also change some variable names to make code easier
to read.
Differential Revision:
https://phab.mercurial-scm.org/D4270
