D5290: branchmap: refactor for better encapsulation

[yuja (Yuya Nishihara)]

yuja added a comment.


  Can you split this to a couple of patches?
  
  The idea sounds good, but it isn't easy to review formatting changes,
  code moves, and interface improvements as a single patch.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D5290

To: mjpieters, #hg-reviewers
Cc: yuja, mercurial-devel