Add ability to specify and run post upload hooks.

Motivation: There are a few things we want to do in Skia infrastructure that is not possible to do without this functionality.
Eg1: If there is a change made to Skia's markdown then automatically include a 'DOCS_PREVIEW_URL=https://skia.org?cl=1234' in the CL's description.
Eg2: Automatically add 'NOTRY=true' for changes impacting things that do not need trybot runs.
Eg3: Include CL specific links to skia's perf (https://perf.skia.org/) and correctness (https://gold.skia.org/) servers.

BUG=chromium:462208

Review URL: https://codereview.chromium.org/949273002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@294242 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/tests/git_cl_test.py b/tests/git_cl_test.py
index 94cd662..ed29824 100755
--- a/tests/git_cl_test.py
+++ b/tests/git_cl_test.py
@@ -221,6 +221,7 @@
         ((['git', 'symbolic-ref', 'HEAD'],), 'hash'),
         ((['git',
            'config', 'branch.hash.last-upload-hash', 'hash'],), ''),
+        ((['git', 'config', 'rietveld.run-post-upload-hook'],), ''),
     ]
 
   @staticmethod
@@ -731,6 +732,8 @@
            'rietveld.project'],), ''),
         ((['git', 'config', '--unset-all',
            'rietveld.pending-ref-prefix'],), ''),
+        ((['git', 'config', '--unset-all',
+           'rietveld.run-post-upload-hook'],), ''),
         ((['git', 'config', 'gerrit.host',
            'gerrit.chromium.org'],), ''),
         # DownloadHooks(False)
@@ -758,6 +761,8 @@
         # DownloadHooks(True)
         ((['git', 'config', 'rietveld.bug-prefix'],), ''),
         (('Bug Prefix:',), ''),
+        ((['git', 'config', 'rietveld.run-post-upload-hook'],), ''),
+        (('Run Post Upload Hook:',), ''),
         ((commit_msg_path, os.X_OK,), True),
         ]
     git_cl.main(['config'])