ci: add custom parameter for pull request

This will allow us to index tasks by pull request which can help testing
changes in external repos.

Author: ahal

taskcluster/self_taskgraph/custom_parameters.py

@@ -2,7 +2,30 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+import os
+
+from voluptuous import All, Any, Range, Required
+
+from taskgraph.parameters import extend_parameters_schema
+
+
+def get_defaults(repo_root):
+    return {
+        "pull_request_number": None,
+    }
+
+
+extend_parameters_schema(
+    {
+        Required("pull_request_number"): Any(All(int, Range(min=1)), None),
+    },
+    defaults_fn=get_defaults,
+)
+
 
 def decision_parameters(graph_config, parameters):
     if parameters["tasks_for"] == "github-release":
         parameters["target_tasks_method"] = "release"
+
+    pr_number = os.environ.get("TASKGRAPH_PULL_REQUEST_NUMBER", None)
+    parameters["pull_request_number"] = None if pr_number is None else int(pr_number)

taskcluster/test/params/main-repo-pull-request-untrusted.yml

@@ -17,6 +17,7 @@ moz_build_date: '20220421203159'
 optimize_target_tasks: true
 owner: [email protected]
 project: taskgraph
+pull_request_number: 123
 pushdate: 0
 pushlog_id: '0'
 repository_type: git

taskcluster/test/params/main-repo-pull-request.yml

@@ -17,6 +17,7 @@ moz_build_date: '20220421203159'
 optimize_target_tasks: true
 owner: [email protected]
 project: taskgraph
+pull_request_number: 123
 pushdate: 0
 pushlog_id: '0'
 repository_type: git