D7122: copies: avoid instancing more changectx to access parent revisions

[martinvonz (Martin von Zweigbergk)]

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


  In my copies-in-changesets version of mozilla-unified, this makes a very significant difference:
  
    before:
    ! wall 4.485065 comb 4.490000 user 4.440000 sys 0.050000 (best of 10)
    after:
    ! wall 3.695755 comb 3.690000 user 3.660000 sys 0.030000 (best of 10)

REPOSITORY
  rHG Mercurial

CHANGES SINCE LAST ACTION
  https://phab.mercurial-scm.org/D7122/new/

REVISION DETAIL
  https://phab.mercurial-scm.org/D7122

To: marmoute, #hg-reviewers, martinvonz
Cc: martinvonz, mercurial-devel