Add option to collapse symlinks in isolate.py

client/isolated_format.py

Index: client/isolated_format.py
diff --git a/client/isolated_format.py b/client/isolated_format.py
index 5c933095b20a09fd944e66904554729ddc34e741..0216a390eb4f6601d249d42afe308b8eb2a2ee9a 100644
--- a/client/isolated_format.py
+++ b/client/isolated_format.py
@@ -309,7 +309,8 @@ def expand_directories_and_symlinks(
 
 
 @tools.profile
-def file_to_metadata(filepath, prevdict, read_only, algo):
+def file_to_metadata(
+    filepath, prevdict, read_only, algo, collapse_symlinks=False):

[M-A Ruel, 2017/04/27 17:44:02]

no default please

[kjlubick, 2017/04/27 17:55:37]

Done.

   """Processes an input file, a dependency, and return meta data about it.
 
   Behaviors:
@@ -340,7 +341,13 @@ def file_to_metadata(filepath, prevdict, read_only, algo):
   # There is the risk of the file's timestamp being reset to its last value
   # manually while its content changed. We don't protect against that use case.
   try:
-    filestats = os.lstat(filepath)
+    filestats = None

[M-A Ruel, 2017/04/27 17:44:02]

not needed

[kjlubick, 2017/04/27 17:55:37]

Done.

+    if collapse_symlinks:
+      # os.stat follows symbolic links
+      filestats = os.stat(filepath)
+    else:
+      # os.lstat does not follow symbolic links, and thus preserves them.
+      filestats = os.lstat(filepath)
   except OSError:
     # The file is not present.
     raise MappingError('%s is missing' % filepath)