support &subdirectory option with freeze and git

CHANGES.txt

@@ -75,6 +75,9 @@
   and when ``package_dir`` is used, so ``pip freeze`` works in more
   cases (:pull:`3258`)
 
+* Correctly freeze Git develop packages in presence of the &subdirectory
+  option (:pull:`3258`)
+
 
 **7.1.2 (2015-08-22)**
 

pip/vcs/git.py

@@ -188,6 +188,33 @@ class Git(VersionControl):
                 rv[ref_name] = commit
         return rv
 
+    def _get_subdirectory(self, location):
+        """Return the relative path of setup.py to the git repo root."""
+        # find the repo root
+        git_dir = self.run_command(['rev-parse', '--git-dir'],
+                                   show_stdout=False, cwd=location).strip()
+        if not os.path.isabs(git_dir):
+            git_dir = os.path.join(location, git_dir)
+        root_dir = os.path.join(git_dir, '..')
+        # find setup.py
+        orig_location = location
+        while not os.path.exists(os.path.join(location, 'setup.py')):
+            last_location = location
+            location = os.path.dirname(location)
+            if location == last_location:
+                # We've traversed up to the root of the filesystem without
+                # finding setup.py
+                logger.warning(
+                    "Could not find setup.py for directory %s (tried all "
+                    "parent directories)",
+                    orig_location,
+                )
+                return None
+        # relative path of setup.py to repo root
+        if os.path.samefile(root_dir, location):
+            return None
+        return os.path.relpath(location, root_dir)
+
     def get_src_requirement(self, dist, location, find_tags):
         repo = self.get_url(location)
         if not repo.lower().startswith('git:'):
@@ -214,7 +241,11 @@ class Git(VersionControl):
         else:
             full_egg_name = '%s-dev' % egg_project_name
 
-        return '%s@%s#egg=%s' % (repo, current_rev, full_egg_name)
+        req = '%s@%s#egg=%s' % (repo, current_rev, full_egg_name)
+        subdirectory = self._get_subdirectory(location)
+        if subdirectory:
+            req += '&subdirectory=' + subdirectory
+        return req
 
     def get_url_rev(self):
         """