Use gclient's git_cache setting in bot_update/api.py

recipe_modules/gclient/config.py

 # Copyright 2013 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.
 
 import types
 
 from recipe_engine.config import config_item_context, ConfigGroup, BadConf
 from recipe_engine.config import ConfigList, Dict, Single, Static, Set, List
 
 from . import api as gclient_api
 
 
 def BaseConfig(USE_MIRROR=True, GIT_MODE=False, CACHE_DIR=None,
                PATCH_PROJECT=None, BUILDSPEC_VERSION=None,
                **_kwargs):
   deps = '.DEPS.git' if GIT_MODE else 'DEPS'
-  cache_dir = str(CACHE_DIR) if GIT_MODE and CACHE_DIR else None
+  cache_dir = str(CACHE_DIR) if GIT_MODE and CACHE_DIR else ''
   return ConfigGroup(
     solutions = ConfigList(
       lambda: ConfigGroup(
         name = Single(basestring),
         url = Single(basestring),
         deps_file = Single(basestring, empty_val=deps, required=False,
                            hidden=False),
         managed = Single(bool, empty_val=True, required=False, hidden=False),
         custom_deps = Dict(value_type=(basestring, types.NoneType)),
         custom_vars = Dict(value_type=basestring),
         safesync_url = Single(basestring, required=False),
 
         revision = Single(
             (basestring, gclient_api.RevisionResolver),
             required=False, hidden=True),
       )
     ),
     deps_os = Dict(value_type=basestring),
     hooks = List(basestring),
     target_os = Set(basestring),
     target_os_only = Single(bool, empty_val=False, required=False),
-    cache_dir = Static(cache_dir, hidden=False),
+    cache_dir = Single(
+        basestring, empty_val=cache_dir, required=False, hidden=False),
 
     # If supplied, use this as the source root (instead of the first solution's
     # checkout).
     src_root = Single(basestring, required=False, hidden=True),
 
     # Maps 'solution' -> build_property
     got_revision_mapping = Dict(hidden=True),
 
     # Addition revisions we want to pass in.  For now theres a duplication
     # of code here of setting custom vars AND passing in --revision. We hope
@@ skipping 112 matching lines @@
 @config_ctx(includes=['chromium_bare'])
 def chromium_empty(c):
   c.solutions[0].deps_file = ''  # pragma: no cover
 
 @config_ctx(includes=['chromium_bare'])
 def chromium(c):
   s = c.solutions[0]
   s.custom_deps = mirror_only(c, {})
 
 @config_ctx(includes=['chromium'])
+def chromium_no_git_cache(c):
+  c.cache_dir = ''
+
+@config_ctx(includes=['chromium'])
 def chromium_lkcr(c):
   # TODO(phajdan.jr): Add git hashes for LKCR crbug.com/349277.
   if c.GIT_MODE:
     raise BadConf('Git has problems with safesync_url and LKCR, '
                   'crbug.com/349277 crbug.com/109191')  # pragma: no cover
   s = c.solutions[0]
   s.safesync_url = 'https://build.chromium.org/p/chromium/lkcr-status/lkgr'
   # TODO(hinoka): Once lkcr exists and is a tag, it should just be lkcr
   #               rather than origin/lkcr.
   s.revision = 'origin/lkcr'
@@ skipping 460 matching lines @@
   soln = c.solutions.add()
   soln.name = 'gerrit-test-cq-normal'
   soln.url = 'https://chromium.googlesource.com/playground/gerrit-cq/normal.git'
 
 # TODO(phajdan.jr): Move to proper repo and add coverage.
 @config_ctx()
 def valgrind(c):  # pragma: no cover
   """Add Valgrind binaries to the gclient solution."""
   c.solutions[0].custom_deps['src/third_party/valgrind'] = \
     ChromiumGitURL(c, 'chromium', 'deps', 'valgrind', 'binaries')