Remove trailing slash on drive path

AUTHORS

@@ -24,5 +24,6 @@ Contributors are:
 -Alexis Horgix Chotard
 -Piotr Babij <piotr.babij _at_ gmail.com>
 -Mikuláš Poul <mikulaspoul _at_ gmail.com>
+-Charles Bouchard-Légaré <cblegare.atl _at_ ntis.ca>
 
 Portions derived from other open source works and are clearly marked.

git/objects/submodule/base.py

@@ -278,7 +278,7 @@ def _to_relative_path(cls, parent_repo, path):
             if not path.startswith(working_tree_linux):
                 raise ValueError("Submodule checkout path '%s' needs to be within the parents repository at '%s'"
                                  % (working_tree_linux, path))
-            path = path[len(working_tree_linux) + 1:]
+            path = path[len(working_tree_linux.rstrip('/')) + 1:]
             if not path:
                 raise ValueError("Absolute submodule path '%s' didn't yield a valid relative path" % path)
             # end verify converted relative path makes sense

git/test/test_submodule.py

@@ -10,7 +10,7 @@
 
 import git
 from git.cmd import Git
-from git.compat import string_types
+from git.compat import string_types, is_win
 from git.exc import (
     InvalidGitRepositoryError,
     RepositoryDirtyError
@@ -911,3 +911,13 @@ def test_branch_renames(self, rw_dir):
         parent_repo.submodule_update(to_latest_revision=True, force_reset=True)
         assert sm_mod.commit() == sm_pfb.commit, "Now head should have been reset"
         assert sm_mod.head.ref.name == sm_pfb.name
+
+    @skipIf(not is_win, "Specifically for Windows.")
+    def test_to_relative_path_with_super_at_root_drive(self):
+        class Repo(object):
+            working_tree_dir = 'D:\\'
+        super_repo = Repo()
+        submodule_path = 'D:\\submodule_path'
+        relative_path = Submodule._to_relative_path(super_repo, submodule_path)
+        msg = '_to_relative_path should be "submodule_path" but was "%s"' % relative_path
+        assert relative_path == 'submodule_path', msg