diff --git a/project.py b/project.py
index 5058088..d54e336 100644
--- a/project.py
+++ b/project.py
@@ -1583,8 +1583,6 @@
 
     if kill:
       old = self.bare_git.GetHead()
-      if old is None:
-        old = 'refs/heads/please_never_use_this_as_a_branch_name'
 
       try:
         self.bare_git.DetachHead(rev)
@@ -1596,7 +1594,10 @@
                        capture_stderr=True)
         b.Wait()
       finally:
-        self.bare_git.SetHead(old)
+        if ID_RE.match(old):
+          self.bare_git.DetachHead(old)
+        else:
+          self.bare_git.SetHead(old)
         left = self._allrefs
 
       for branch in kill:
diff --git a/subcmds/rebase.py b/subcmds/rebase.py
index 1bdc1f0..7479697 100644
--- a/subcmds/rebase.py
+++ b/subcmds/rebase.py
@@ -54,6 +54,11 @@
     p.add_option('--auto-stash',
                  dest='auto_stash', action='store_true',
                  help='Stash local modifications before starting')
+    p.add_option('-m', '--onto-manifest',
+                 dest='onto_manifest', action='store_true',
+                 help='Rebase onto the manifest version instead of upstream '
+                      'HEAD.  This helps to make sure the local tree stays '
+                      'consistent if you previously synced to a manifest.')
 
   def Execute(self, opt, args):
     all_projects = self.GetProjects(args)
@@ -106,6 +111,10 @@
       if opt.interactive:
         args.append("-i")
 
+      if opt.onto_manifest:
+        args.append('--onto')
+        args.append(project.revisionExpr)
+
       args.append(upbranch.LocalMerge)
 
       print('# %s: rebasing %s -> %s'
diff --git a/subcmds/start.py b/subcmds/start.py
index 940c341..d1430a9 100644
--- a/subcmds/start.py
+++ b/subcmds/start.py
@@ -57,10 +57,15 @@
         print("error: at least one project must be specified", file=sys.stderr)
         sys.exit(1)
 
+    all_projects = self.GetProjects(projects,
+                                    missing_ok=bool(self.gitc_manifest))
+
+    # This must happen after we find all_projects, since GetProjects may need
+    # the local directory, which will disappear once we save the GITC manifest.
     if self.gitc_manifest:
-      all_projects = self.GetProjects(projects, manifest=self.gitc_manifest,
-                                      missing_ok=True)
-      for project in all_projects:
+      gitc_projects = self.GetProjects(projects, manifest=self.gitc_manifest,
+                                       missing_ok=True)
+      for project in gitc_projects:
         if project.old_revision:
           project.already_synced = True
         else:
@@ -70,8 +75,10 @@
       # Save the GITC manifest.
       gitc_utils.save_manifest(self.gitc_manifest)
 
-    all_projects = self.GetProjects(projects,
-                                    missing_ok=bool(self.gitc_manifest))
+      # Make sure we have a valid CWD
+      if not os.path.exists(os.getcwd()):
+        os.chdir(self.manifest.topdir)
+
     pm = Progress('Starting %s' % nb, len(all_projects))
     for project in all_projects:
       pm.update()