--- a/hgext/rebase.py	Sun Oct 15 20:36:29 2017 -0700
+++ b/hgext/rebase.py	Sun Oct 15 20:36:29 2017 -0700
@@ -977,10 +977,11 @@
         repo.ui.debug("   detach base %d:%s\n" % (base, repo[base]))
     # When collapsing in-place, the parent is the common ancestor, we
     # have to allow merging with it.
+    wctx = repo[None]
     stats = mergemod.update(repo, rev, True, True, base, collapse,
                             labels=['dest', 'source'])
     if collapse:
-        copies.duplicatecopies(repo, rev, dest)
+        copies.duplicatecopies(repo, wctx, rev, dest)
     else:
         # If we're not using --collapse, we need to
         # duplicate copies between the revision we're
@@ -988,7 +989,7 @@
         # duplicate any copies that have already been
         # performed in the destination.
         p1rev = repo[rev].p1().rev()
-        copies.duplicatecopies(repo, rev, p1rev, skiprev=dest)
+        copies.duplicatecopies(repo, wctx, rev, p1rev, skiprev=dest)
     return stats
 
 def adjustdest(repo, rev, destmap, state, skipped):

--- a/mercurial/context.py	Sun Oct 15 20:36:29 2017 -0700
+++ b/mercurial/context.py	Sun Oct 15 20:36:29 2017 -0700
@@ -1935,6 +1935,11 @@
         self._repo.wwrite(self._path, data, flags,
                           backgroundclose=backgroundclose)
 
+    def markcopied(self, src):
+        """marks this file a copy of `src`"""
+        if self._repo.dirstate[self._path] in "nma":
+            self._repo.dirstate.copy(src, self._path)
+
     def clearunknown(self):
         """Removes conflicting items in the working directory so that
         ``write()`` can be called successfully.

--- a/mercurial/copies.py	Sun Oct 15 20:36:29 2017 -0700
+++ b/mercurial/copies.py	Sun Oct 15 20:36:29 2017 -0700
@@ -842,7 +842,7 @@
                         data['incompletediverge'][sf] = [of, f]
                     return
 
-def duplicatecopies(repo, rev, fromrev, skiprev=None):
+def duplicatecopies(repo, wctx, rev, fromrev, skiprev=None):
     '''reproduce copies from fromrev to rev in the dirstate
 
     If skiprev is specified, it's a revision that should be used to
@@ -863,5 +863,4 @@
         # actually be in the dirstate
         if dst in exclude:
             continue
-        if repo.dirstate[dst] in "nma":
-            repo.dirstate.copy(src, dst)
+        wctx[dst].markcopied(src)

--- a/mercurial/merge.py	Sun Oct 15 20:36:29 2017 -0700
+++ b/mercurial/merge.py	Sun Oct 15 20:36:29 2017 -0700
@@ -2001,5 +2001,5 @@
         repo.setparents(repo['.'].node(), pother)
         repo.dirstate.write(repo.currenttransaction())
         # fix up dirstate for copies and renames
-        copies.duplicatecopies(repo, ctx.rev(), pctx.rev())
+        copies.duplicatecopies(repo, repo[None], ctx.rev(), pctx.rev())
     return stats