Merge ~racb/usd-importer:fix-empty-dir-symlink-traversal into usd-importer:master

[Robie Basak]

[Nish Aravamudan (nacc)]

Seems reasonable and with this change websockify successfully imports (at least past the point it failed before).

review: Approve

[Robie Basak (racb)]

I checked that in the fixed import of websockify 0.5.1+dfsg1-1, there is an entry in include/ of:

040000 tree 4b825dc642cb6eb9a060e54bf8d69288fbee4904 web-socket-js-project

so empty directory imports do still appear to be working.

diff --git a/gitubuntu/git_repository.py b/gitubuntu/git_repository.py
index 2b91380..89416b5 100644
--- a/gitubuntu/git_repository.py
+++ b/gitubuntu/git_repository.py
@@ -8,6 +8,7 @@ import logging
 import os
 import re
 import shutil
+import stat
 from subprocess import CalledProcessError
 import sys
 import tempfile
@@ -988,7 +989,9 @@ class GitUbuntuRepository:
         tree_builder = None
         for entry in dir_list:
             entry_path = os.path.join(full_path, entry)
-            if os.path.isdir(entry_path):
+            # We cannot use os.path.isdir() here as we don't want to recurse
+            # down symlinks to directories.
+            if stat.S_ISDIR(os.lstat(entry_path).st_mode):
                 # this is a directory, so recurse down
                 entry_oid = cls._add_missing_tree_dirs(
                     repo=repo,