Add gclient hook that checks local git configuration.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 3a85095625ba2bbf13775dcb6a547526aebfc360..6d5dd5eb4dd95f3687ea5dfa136e45c3b4af0145 100644
--- a/DEPS
+++ b/DEPS
@@ -820,4 +820,16 @@ hooks = [
     "pattern": ".",
     "action": ["python", "src/build/gyp_chromium"],
   },
+  {
+    # Verify committers' ~/.netc, gclient and git are properly configured for
+    # write access to the git repo. To be removed sometime after Chrome to git
+    # migration completes (let's say Sep 1 2014).
+    "name": "check_git_config",
+    "pattern": ".",
+    "action": [
+        "python",
+        "src/tools/check_git_config.py",
+        "--running-as-hook",
+    ],
+  },
 ]