--- a/hgext/evolve.py	Thu Mar 19 12:31:51 2015 -0700
+++ b/hgext/evolve.py	Fri Mar 20 12:51:57 2015 -0700
@@ -1741,6 +1741,7 @@
     [('n', 'new', [], _("successor changeset (DEPRECATED)")),
      ('s', 'succ', [], _("successor changeset")),
      ('r', 'rev', [], _("revisions to prune")),
+     ('k', 'keep', None, _("does not modify working copy during prune")),
      ('', 'biject', False, _("do a 1-1 map between rev and successor ranges")),
      ('B', 'bookmark', '', _("remove revs only reachable from given"
                              " bookmark"))] + metadataopts,
@@ -1833,8 +1834,28 @@
                 newnode = newnode.parents()[0]
 
         if newnode.node() != wdp.node():
-            commands.update(ui, repo, newnode.rev())
-            ui.status(_('working directory now at %s\n') % newnode)
+            if opts.get('keep', False):
+                # This is largely the same as the implementation in
+                # strip.stripcmd(). We might want to refactor this somewhere
+                # common at some point.
+
+                # only reset the dirstate for files that would actually change
+                # between the working context and uctx
+                descendantrevs = repo.revs("%d::." % newnode.rev())
+                changedfiles = []
+                for rev in descendantrevs:
+                    # blindly reset the files, regardless of what actually changed
+                    changedfiles.extend(repo[rev].files())
+
+                # reset files that only changed in the dirstate too
+                dirstate = repo.dirstate
+                dirchanges = [f for f in dirstate if dirstate[f] != 'n']
+                changedfiles.extend(dirchanges)
+                repo.dirstate.rebuild(newnode.node(), newnode.manifest(), changedfiles)
+                repo.dirstate.write()
+            else:
+                commands.update(ui, repo, newnode.rev())
+                ui.status(_('working directory now at %s\n') % newnode)
         # update bookmarks
         if bookmark:
             _deletebookmark(ui, marks, bookmark)