http-cache.diff

diff --git a/pip/download.py b/pip/download.py
index 4c23f5e..f503320 100644
--- a/pip/download.py
+++ b/pip/download.py
@@ -18,6 +18,7 @@ from pip.util import (splitext, rmtree, format_size, display_path,
                       backup_dir, ask_path_exists, unpack_file,
                       create_download_cache_folder, cache_download)
 from pip.vcs import vcs
+from pip.locations import HTTP_CACHE_DIR
 from pip.log import logger
 from pip._vendor import requests, six
 from pip._vendor.requests.adapters import BaseAdapter
@@ -27,6 +28,9 @@ from pip._vendor.requests.exceptions import InvalidURL, ChunkedEncodingError
 from pip._vendor.requests.models import Response
 from pip._vendor.requests.structures import CaseInsensitiveDict
 
+from cachecontrol import CacheControlAdapter
+from cachecontrol.caches import FileCache
+
 __all__ = ['get_file_content',
            'is_url', 'url_to_path', 'path_to_url',
            'is_archive_file', 'unpack_vcs_link',
@@ -225,11 +229,17 @@ class PipSession(requests.Session):
         # Attach our Authentication handler to the session
         self.auth = MultiDomainBasicAuth()
 
+        # Configure our Cache
+        adapter_kw = {"cache": FileCache(HTTP_CACHE_DIR)}
+
         # Configure retries
         if retries:
-            http_adapter = requests.adapters.HTTPAdapter(max_retries=retries)
-            self.mount("http://", http_adapter)
-            self.mount("https://", http_adapter)
+            adapter_kw.update({"max_retries": retries})
+
+        http_adapter = CacheControlAdapter(**adapter_kw)
+
+        self.mount("http://", http_adapter)
+        self.mount("https://", http_adapter)
 
         # Enable file:// urls
         self.mount("file://", LocalFSAdapter())
diff --git a/pip/locations.py b/pip/locations.py
index 7a848cf..17df4d7 100644
--- a/pip/locations.py
+++ b/pip/locations.py
@@ -17,6 +17,9 @@ import pip.exceptions
 install
 
 
+HTTP_CACHE_DIR = os.path.expanduser("~/Library/Caches/pip/http")
+
+
 DELETE_MARKER_MESSAGE = '''\
 This file is placed here by pip to indicate the source was put
 here by pip.