During presubmit, look in parent directories for buildtools/checkdeps.

PRESUBMIT.py

Index: PRESUBMIT.py
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 459d3da755ed1706ab904c4349a2b6f65985759b..5dd22e25f0c522f3d199178e68252a5dd615d3f7 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -19,8 +19,18 @@ def _CheckUnwantedDependencies(input_api, output_api):
   # eval-ed and thus doesn't have __file__.
   original_sys_path = sys.path
   try:
-    sys.path = sys.path + [input_api.os_path.join(
-        input_api.PresubmitLocalPath(), 'buildtools', 'checkdeps')]
+    checkdeps_relpath = input_api.os_path.join('buildtools', 'checkdeps')
+    checkdeps_basepath = input_api.PresubmitLocalPath()
+    checkdeps_path = input_api.os_path.join(checkdeps_basepath,
+                                            checkdeps_relpath)
+    while not input_api.os_path.exists(checkdeps_path):
+      if checkdeps_basepath == input_api.os_path.dirname(checkdeps_basepath):

[Lei Zhang, 2015/11/20 02:57:42]

Well, in theory, /buildtools/checkdeps may contain the checkdeps we are looking
for, but really, that's not gonna happen.

+        raise ImportError('Cannot find checkdeps')
+      checkdeps_basepath = input_api.os_path.dirname(checkdeps_basepath)

[hans, 2015/11/20 03:26:28]

Sorry for being a little slow here.. how does this line work? Does it take
checkdeps_basepath to the parent directory?

[Lei Zhang, 2015/11/20 03:29:19]

It's essentially: foo = os.path.dirname(foo)
https://docs.python.org/2/library/os.path.html

[hans, 2015/11/20 03:52:21]

Ah, I get it now, thanks.

+      checkdeps_path = input_api.os_path.join(checkdeps_basepath,
+                                              checkdeps_relpath)
+
+    sys.path.append(checkdeps_path)
     import checkdeps
     from cpp_checker import CppChecker
     from rules import Rule