Bug 1835689 - don't include cached tasks in existing_tasks for release promotion. r=releng-reviewers,taskgraph-reviewers,bhearsum

Release promotion reuses tasks generated by the on-push decision task,
to avoid duplicating work.  For cached tasks however, that means reusing
index lookups that can be out of date by the time relpro runs, and
requiring a new push to pick up rebuilt cached tasks.  By listing the
cached kinds in rebuild-kinds, we force new index lookups at release
promotion time, to pick up e.g. new docker images without an extra push.

Differential Revision: https://phabricator.services.mozilla.com/D182774

taskcluster/ci/config.yml

@@ -256,6 +256,11 @@ release-promotion:
         - 'devedition'
         - 'fennec'
         - 'firefox'
+    rebuild-kinds:
+        - docker-image
+        - fetch
+        - packages
+        - toolchain
     flavors:
         promote_devedition:
             product: devedition

taskcluster/gecko_taskgraph/actions/release_promotion.py

@@ -128,6 +128,7 @@ def get_flavors(graph_config, param):
                     "Optional: an array of kinds to ignore from the previous "
                     "graph(s)."
                 ),
+                "default": graph_config["release-promotion"].get("rebuild-kinds", []),
                 "items": {
                     "type": "string",
                 },

taskcluster/gecko_taskgraph/config.py

@@ -42,6 +42,7 @@ graph_config_schema = Schema(
                     Optional("partial-updates"): bool,
                 }
             },
+            Optional("rebuild-kinds"): [str],
         },
         Required("merge-automation"): {
             Required("behaviors"): {