D648: blackbox: fix rotation with chg

[yuja (Yuya Nishihara)]

yuja accepted this revision.
yuja added a comment.
This revision is now accepted and ready to land.


  > I think the original patch was trying to make different `ui` objects use a same file object if their `blackbox.log` path is the same. In theory it could also be problematic in the rotation case. Anyway, that should become unnecessary after https://phab.mercurial-scm.org/D650.
  
  Copied this to the commit message and queued the first 5 patches, thanks.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D648

To: quark, #hg-reviewers, durham, yuja
Cc: yuja, durham, mercurial-devel