Add --output option to Swarming client and pass it through to the bot

appengine/swarming/server/task_request.py

Index: appengine/swarming/server/task_request.py
diff --git a/appengine/swarming/server/task_request.py b/appengine/swarming/server/task_request.py
index de0aa0dc7533984c9ddd900d34937571fd573c87..79023af882cbd2a0c781bd1226f2bc216009342a 100644
--- a/appengine/swarming/server/task_request.py
+++ b/appengine/swarming/server/task_request.py
@@ -226,13 +226,21 @@ def _validate_package_version(prop, value):
 
 def _validate_package_path(_prop, path):
   """Validates a CIPD installation path."""
+  if not path:
+    raise datastore_errors.BadValueError(
+        'CIPD package path is required. Use "." to install to run dir.')
   _validate_rel_path('CIPD package path', path)
 
 
+def _validate_output_path(_prop, value):
+  """Validates a path for an output file."""
+  _validate_rel_path('output file', value)
+
+
 def _validate_rel_path(value_name, path):
   if not path:
     raise datastore_errors.BadValueError(
-        '%s is required. Use "." to install to run dir.' % value_name)
+        'No argument provided for %s.' % value_name)
   if '\\' in path:
     raise datastore_errors.BadValueError(
         '%s cannot contain \\. On Windows forward-slashes '
@@ -449,6 +457,12 @@ class TaskProperties(ndb.Model):
   # task.
   idempotent = ndb.BooleanProperty(default=False, indexed=False)
 
+  # A list of outputs expected. If empty, all files written to
+  # $(ISOLATED_OUTDIR) will be returned; otherwise, the files in this list
+  # will be added to those in that directory.
+  outputs = ndb.StringProperty(repeated=True, indexed=False,
+      validator=_validate_output_path)
+
   @property
   def is_terminate(self):
     """If True, it is a terminate request."""