Provide an alternative to os.path.samefile

For windows under python2

Author: xavfernandez

pip/compat/__init__.py

@@ -25,7 +25,7 @@
 
 __all__ = [
     "logging_dictConfig", "ipaddress", "uses_pycache", "console_to_str",
-    "native_str", "get_path_uid", "stdlib_pkgs", "WINDOWS",
+    "native_str", "get_path_uid", "stdlib_pkgs", "WINDOWS", "samefile"
 ]
 
 
@@ -126,3 +126,13 @@ def expanduser(path):
 # windows detection, covers cpython and ironpython
 WINDOWS = (sys.platform.startswith("win") or
            (sys.platform == 'cli' and os.name == 'nt'))
+
+
+def samefile(file1, file2):
+    """Provide an alternative for os.path.samefile on Windows/Python2"""
+    if hasattr(os.path, 'samefile'):
+        return os.path.samefile(file1, file2)
+    else:
+        path1 = os.path.normcase(os.path.abspath(file1))
+        path2 = os.path.normcase(os.path.abspath(file2))
+        return path1 == path2

pip/vcs/git.py

@@ -4,6 +4,7 @@
 import tempfile
 import os.path
 
+from pip.compat import samefile
 from pip.exceptions import BadCommand
 from pip._vendor.six.moves.urllib import parse as urllib_parse
 from pip._vendor.six.moves.urllib import request as urllib_request
@@ -211,7 +212,7 @@ def _get_subdirectory(self, location):
                 )
                 return None
         # relative path of setup.py to repo root
-        if os.path.samefile(root_dir, location):
+        if samefile(root_dir, location):
             return None
         return os.path.relpath(location, root_dir)