Make it possible to use 'cwd' in api.step.context

recipe_engine/recipe_api.py

Index: recipe_engine/recipe_api.py
diff --git a/recipe_engine/recipe_api.py b/recipe_engine/recipe_api.py
index d2c1d8b81b11bda4c222115e30095cf7593ec392..f0226221501b123e267e93b65b0574474bf37533 100644
--- a/recipe_engine/recipe_api.py
+++ b/recipe_engine/recipe_api.py
@@ -118,6 +118,7 @@ class AggregatedStepFailure(StepFailure):
 
 _FUNCTION_REGISTRY = {
   'aggregated_result': {'combine': lambda a, b: b},
+  'cwd': {'combine': lambda a, b: b},

[Sergiy Byelozyorov, 2016/06/29 13:56:30]

This would always return value passed second and never return whatever is in the
compositor... what's the point?

[Paweł Hajdan Jr., 2016/06/29 13:57:57]

See other entries here which already do this. The meaning of that is to
override/overwrite value in compositor.

[Sergiy Byelozyorov, 2016/06/29 14:00:10]

But the point is that it doesn't... it just returns the second value without
ever considering the value in the compositor. And it does not update the value
in the compositor either:
https://cs.chromium.org/chromium/infra/recipes-py/recipe_engine/field_compose....

[Paweł Hajdan Jr., 2016/06/29 14:14:31]

While I have to provide a combine function here, I've simplified step recipe
module code based on your suggestion. PTAL.

   'env': {'combine': lambda a, b: dict(a, **b)},
   'name': {'combine': lambda a, b: '%s.%s' % (a, b)},
   'nest_level': {'combine': lambda a, b: a + b},