Add src_root attribute to support installing from a copy.

--HG--
branch : distribute
extra : rebase_source : 95242b20ab228862aeef205f399869f79e342f0e

setuptools/command/build_py.py

@@ -157,9 +157,11 @@ class build_py(_build_py):
         _build_py.initialize_options(self)
 
 
-
-
-
+    def get_package_dir(self, package):
+        res = _build_py.get_package_dir(self, package)
+        if self.distribution.src_root is not None:
+            return os.path.join(self.distribution.src_root, res)
+        return res
 
 
     def exclude_data_files(self, package, src_dir, files):

setuptools/dist.py

@@ -210,6 +210,7 @@ class Distribution(_Distribution):
         self.require_features = []
         self.features = {}
         self.dist_files = []
+        self.src_root = attrs.pop("src_root")
         self.patch_missing_pkg_info(attrs)
         # Make sure we have any eggs needed to interpret 'attrs'
         if attrs is not None: