rebase: ignore negative state when updating back to original wc parent

The state mapping also contains some magic negative values (detached
parent, ignored revision). Blindly reading the state thus lead to
unfortunate usage of the negative value as an update destination. We
now filter them out.

We do a minor alteration of the test to catch this.

hgext/rebase.py

@@ -449,6 +449,9 b' def rebase(ui, repo, **opts):'
         # restore original working directory
         # (we do this before stripping)
         newwd = state.get(originalwd, originalwd)
+        if newwd < 0:
+            # original directory is a parent of rebase set root or ignored
+            newwd = originalwd
         if newwd not in [c.rev() for c in repo[None].parents()]:
             ui.note(_("update back to initial working directory parent\n"))
             hg.updaterepo(repo, newwd, False)

tests/test-rebase-scenario-global.t

@@ -300,8 +300,12 b' Check rebasing public changeset'
 
 Check rebasing mutable changeset
 Source phase greater or equal to destination phase: new changeset get the phase of source:
+  $ hg id -n
+  5
   $ hg rebase -s9 -d0
   saved backup bundle to $TESTTMP/a7/.hg/strip-backup/2b23e52411f4-backup.hg (glob)
+  $ hg id -n # check we updated back to parent
+  5
   $ hg log --template "{phase}\n" -r 9
   draft
   $ hg rebase -s9 -d1