Early exit auto-update when running as root.

update_depot_tools

 #!/usr/bin/env bash
 # Copyright (c) 2010 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This script will try to sync the bootstrap directories and then defer control.
 
+if [ "$USER" == "root" ];
+then
+  echo Running depot tools as root is sad.
+  exit
+fi
+
 base_dir=$(dirname "$0")
 if [ -L "$base_dir" ]
 then
     base_dir=`cd "$base_dir" && pwd -P`
 fi
 
 # Test git and git --version.
 function test_git {
   local GITV="$(git --version)" || {
     echo "git isn't installed, please install it"
@@ skipping 48 matching lines @@
 then
   # Update the bootstrap directory to stay up-to-date with the latest
   # depot_tools.
   BEFORE_REVISION=$(get_svn_revision)
   svn -q up "$base_dir"
   AFTER_REVISION=$(get_svn_revision)
   if [[ "$BEFORE_REVISION" != "$AFTER_REVISION" ]]; then
     echo "Depot Tools has been updated to revision $AFTER_REVISION." 1>&2
   fi
 fi