D4206: changegroup: extract cgpacker.group() to standalone function

[durin42 (Augie Fackler)]

durin42 added inline comments.

INLINE COMMENTS

> changegroup.py:690
> +    """Calculate a delta group, yielding a sequence of changegroup chunks
> +    (strings).
> +

nit: bytes

(follow-up please, to avoid turnaround time issues)

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D4206

To: indygreg, #hg-reviewers
Cc: durin42, mercurial-devel