bisect-kit: skip recently added overlays

'cros_mark_as_stable' expects all overlays is recorded in manifest file.
Before we synthesize manifest files for each intra versions, ignore
these overlays first.

BUG=b:129723001
TEST=./switch_cros_localbuild.py 'R75-11996.0.0~R75-11997.0.0/40'

Change-Id: Id09c554ba7b25102e606969e269aeb2809caf42d
Reviewed-on: https://chromium-review.googlesource.com/1545617
Commit-Ready: Kuang-che Wu <kcwu@chromium.org>
Tested-by: Kuang-che Wu <kcwu@chromium.org>
Reviewed-by: Chung-yih Wang <cywang@chromium.org>
diff --git a/bisect_kit/repo_util.py b/bisect_kit/repo_util.py
index c923d78..6b9a760 100644
--- a/bisect_kit/repo_util.py
+++ b/bisect_kit/repo_util.py
@@ -280,6 +280,18 @@
                                             end_time, parse_dependencies)
 
 
+def projects_in_manifest(repo_root):
+  manifest_dir = os.path.join(repo_root, '.repo', 'manifests')
+  manifest_file = os.path.join(repo_root, '.repo', 'manifest.xml')
+  parser = ManifestParser(manifest_dir)
+  manifest = open(manifest_file).read()
+  root = parser.parse_single_xml(manifest)
+  result = []
+  for node in root.findall('.//project'):
+    result.append(node.get('path', node.get('name')))
+  return result
+
+
 class RepoMirror(codechange.CodeStorage):
   """Repo git mirror."""