diff --git a/mercurial/copies.py b/mercurial/copies.py --- a/mercurial/copies.py +++ b/mercurial/copies.py @@ -268,15 +268,19 @@ childcopies = { dst: src for dst, src in childcopies.items() if match(dst) } - # Copy the dict only if later iterations will also need it - if i != len(children[r]) - 1: - newcopies = copies.copy() - else: - newcopies = copies + newcopies = copies if childcopies: newcopies = _chain(newcopies, childcopies) + # _chain makes a copies, we can avoid doing so in some + # simple/linear cases. + assert newcopies is not copies for f in removed: if f in newcopies: + if newcopies is copies: + # copy on write to avoid affecting potential other + # branches. when there are no other branches, this + # could be avoided. + newcopies = copies.copy() del newcopies[f] othercopies = all_copies.get(c) if othercopies is None: