unify helper vars across all sections

Make it easier for PREUPLOAD.cfg writers to access any of the replacement
vars in different contexts rather than making them section-specific.

Bug: 32317688
Test: a modified PREUPLOAD.cfg with $REPO_ROOT in Hook Scripts works
Test: ran the new hooks_unittest!
Change-Id: I20dac8eeff78ce4f062dbaf8f7354df420e82d7d
diff --git a/pre-upload.py b/pre-upload.py
index cc8d24a..f15a9b7 100755
--- a/pre-upload.py
+++ b/pre-upload.py
@@ -23,7 +23,6 @@
 from __future__ import print_function
 
 import argparse
-import collections
 import os
 import sys
 
@@ -38,6 +37,7 @@
     sys.path.insert(0, _path)
 del _path
 
+import rh
 import rh.results
 import rh.config
 import rh.git
@@ -50,9 +50,6 @@
 REPOHOOKS_URL = 'https://android.googlesource.com/platform/tools/repohooks/'
 
 
-Project = collections.namedtuple('Project', ['name', 'dir', 'remote'])
-
-
 class Output(object):
     """Class for reporting hook status."""
 
@@ -219,7 +216,7 @@
     })
 
     output = Output(project_name, len(hooks))
-    project = Project(name=project_name, dir=proj_dir, remote=remote)
+    project = rh.Project(name=project_name, dir=proj_dir, remote=remote)
 
     if not commit_list:
         commit_list = rh.git.get_commits(