bug 1442793 - add artifact_prefix attribute. r=bhearsum

MozReview-Commit-ID: GrAiC3sUaEp

--HG--
extra : rebase_source : 62267a238fa9054009351832d6e8326cbc0c4c27

taskcluster/docs/attributes.rst

@@ -203,3 +203,10 @@ Using the "snowman model", we depend on previous graphs if they're defined. So i
 ask for a ``push`` (the head of the snowman) and point at the body and base, we only
 build the head. If we don't point at the body and base, we build the whole snowman
 (build, promote, push).
+
+artifact_prefix
+===============
+Most taskcluster artifacts are public, so we've hardcoded ``public/build`` in a
+lot of places. To support private artifacts, we've moved this to the
+``artifact_prefix`` attribute. It will default to ``public/build`` but will be
+overrideable per-task.

taskcluster/taskgraph/util/attributes.py

@@ -29,7 +29,12 @@ RELEASE_PROMOTION_PROJECTS = {
 } | RELEASE_PROJECTS
 
 _OPTIONAL_ATTRIBUTES = (
-    'nightly', 'signed', 'l10n_chunk', 'shipping_product', 'shipping_phase'
+    'artifact_prefix',
+    'l10n_chunk',
+    'nightly',
+    'signed',
+    'shipping_phase',
+    'shipping_product',
 )