Add git-cl and git-try stubs.

They automatically git clone the original repository and execute the original script. So if they are first in the path, they will be executed. If a user has another git-cl/try in the path prior, these stubs won't be used at all and won't mess with the user's setup.

Also fix a bug with git handling in trychange.py
Review URL: http://codereview.chromium.org/119244

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@17737 0039d316-1c4b-4281-b951-d872f2087c98

git-cl

+#!/bin/sh
+# Copyright (c) 2009 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.
+
+base_dir=$(dirname "$0")
+
+if [ ! -f "$base_dir/git-cl-repo/git-cl" ]; then
+  git clone git://neugierig.org/git-cl.git $base_dir/git-cl-repo
+fi
+
+$base_dir/git-cl-repo/git-cl "$*"

git-try

+#!/bin/sh
+# Copyright (c) 2009 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.
+
+base_dir=$(dirname "$0")
+
+if [ ! -f "$base_dir/git-try-repo/git-try" ]; then
+  git clone git://neugierig.org/git-try.git $base_dir/git-try-repo
+fi
+
+$base_dir/git-try-repo/git-try "$*"