deps2git: Add support for overriding DEPS vars

deps_utils.py

Index: deps_utils.py
===================================================================
--- deps_utils.py	(revision 292133)
+++ deps_utils.py	(working copy)
@@ -16,22 +16,26 @@
 class VarImpl(object):
   """Implement the Var function used within the DEPS file."""
 
-  def __init__(self, local_scope):
+  def __init__(self, local_scope, var_overrides=None):
     self._local_scope = local_scope
+    self._var_overrides = var_overrides or {}
 
   def Lookup(self, var_name):
     """Implements the Var syntax."""
+    if var_name in self._var_overrides:
+      return self._var_overrides[var_name]
     if var_name in self._local_scope.get('vars', {}):
       return self._local_scope['vars'][var_name]
     raise Exception('Var is not defined: %s' % var_name)
 
 
-def GetDepsContent(deps_path):
+def GetDepsContent(deps_path, var_overrides=None):
   """Read a DEPS file and return all the sections."""
   deps_file = open(deps_path, 'rU')
+  var_overrides = var_overrides or {}
   content = deps_file.read()
   local_scope = {}
-  var = VarImpl(local_scope)
+  var = VarImpl(local_scope, var_overrides)
   global_scope = {
       'Var': var.Lookup,
       'deps': {},
@@ -48,6 +52,7 @@
   local_scope.setdefault('skip_child_includes', [])
   local_scope.setdefault('hooks', [])
   local_scope.setdefault('vars', {})
+  local_scope['vars'].update(var_overrides)
 
   return (local_scope['deps'], local_scope['deps_os'],
           local_scope['include_rules'], local_scope['skip_child_includes'],