Add gclient hook that checks local git configuration.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 3a85095625ba2bbf13775dcb6a547526aebfc360..845ab9e1876223ac73daac9d4f022c116f5cb62c 100644
--- a/DEPS
+++ b/DEPS
@@ -815,6 +815,19 @@ hooks = [
     ],
   },
   {
+    # 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). It will probably stay on HEAD
+    # of SVN history forever though.

[iannucci, 2014/08/19 00:42:29]

can drop the last sentence :)

[Vadim Sh., 2014/08/19 00:57:43]

Done.

+    "name": "check_git_config",
+    "pattern": ".",
+    "action": [
+        "python",
+        "src/tools/check_git_config.py",
+        "--running-as-hook",
+    ],
+  },
+  {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "name": "gyp",
     "pattern": ".",