1 files changed, 15 insertions, 1 deletions

diff --git a/project.py b/project.py
index b7ed6f33..faa6b32b 100644
--- a/project.py
+++ b/project.py
@@ -49,6 +49,9 @@ MAXIMUM_RETRY_SLEEP_SEC = 3600.0
 # +-10% random jitter is added to each Fetches retry sleep duration.
 RETRY_JITTER_PERCENT = 0.1
 
+# Whether to use alternates.
+# TODO(vapier): Remove knob once behavior is verified.
+_ALTERNATES = os.environ.get('REPO_USE_ALTERNATES') == '1'
 
 def _lwrite(path, content):
   lock = '%s.lock' % path
@@ -460,7 +463,7 @@ class RemoteSpec(object):
 
 class Project(object):
   # These objects can be shared between several working trees.
-  shareable_dirs = ['hooks', 'objects', 'rr-cache']
+  shareable_dirs = ['hooks', 'rr-cache']
 
   def __init__(self,
                manifest,
@@ -1143,6 +1146,17 @@ class Project(object):
       self._UpdateHooks(quiet=quiet)
     self._InitRemote()
 
+    if _ALTERNATES or self.manifest.is_multimanifest:
+      # If gitdir/objects is a symlink, migrate it from the old layout.
+      gitdir_objects = os.path.join(self.gitdir, 'objects')
+      if platform_utils.islink(gitdir_objects):
+        platform_utils.remove(gitdir_objects, missing_ok=True)
+      gitdir_alt = os.path.join(self.gitdir, 'objects/info/alternates')
+      if not os.path.exists(gitdir_alt):
+        os.makedirs(os.path.dirname(gitdir_alt), exist_ok=True)
+        _lwrite(gitdir_alt, os.path.join(
+            os.path.relpath(self.objdir, gitdir_objects), 'objects') + '\n')
+
     if is_new:
       alt = os.path.join(self.objdir, 'objects/info/alternates')
       try: