rebase: do not cleanup the working copy when --dry-run is used (issue6802)

Since we did not touch the working copy, we don't need to clean it up. This
will avoid wiping exiting changes out.

hgext/rebase.py

@@ -838,6 +838,7 b' class rebaseruntime:'
                 cleanup = False
 
             if cleanup:
+
                 if rebased:
                     strippoints = [
                         c.node() for c in repo.set(b'roots(%ld)', rebased)
@@ -846,13 +847,17 b' class rebaseruntime:'
                 updateifonnodes = set(rebased)
                 updateifonnodes.update(self.destmap.values())
 
-                if not dryrun and not confirm:
+                if not confirm:
+                    # note: when dry run is set the `rebased` and `destmap`
+                    # variables seem to contain "bad" contents, so do not
+                    # rely on them. As dryrun does not need this part of
+                    # the cleanup, this is "fine"
                     updateifonnodes.add(self.originalwd)
 
                 shouldupdate = repo[b'.'].rev() in updateifonnodes
 
                 # Update away from the rebase if necessary
-                if shouldupdate:
+                if not dryrun and shouldupdate:
                     mergemod.clean_update(repo[self.originalwd])
 
                 # Strip from the first rebased revision

tests/test-rebase-dry-run.t

@@ -83,17 +83,15 b' f03 is modified'
   committing changelog
   rebase merging completed
   dry-run rebase completed successfully; run without -n/--dry-run to perform this rebase
-  resolving manifests (known-bad-output !)
-  getting f03.txt (known-bad-output !)
 
 f03 changes are lost
 
   $ hg st
-  M f03.txt (missing-correct-output !)
+  M f03.txt
   $ hg diff
-  diff -r ab62441498e5 f03.txt (missing-correct-output !)
-  --- a/f03.txt	Thu Jan 01 00:00:00 1970 +0000 (missing-correct-output !)
-  +++ b/f03.txt	Thu Jan 01 00:00:00 1970 +0000 (missing-correct-output !)
-  @@ -1,1 +1,2 @@ (missing-correct-output !)
-   three (missing-correct-output !)
-  +add-to-three (missing-correct-output !)
+  diff -r ab62441498e5 f03.txt
+  --- a/f03.txt	Thu Jan 01 00:00:00 1970 +0000
+  +++ b/f03.txt	Thu Jan 01 00:00:00 1970 +0000
+  @@ -1,1 +1,2 @@
+   three
+  +add-to-three