Set project_trigger_overrides to trigger branch builders.

(cherry picked from commit b2d7d5eb3cab76d97b381040f217f82456d3b587)

Bug: 1056428
Change-Id: I53a06c4fa23faec756e303372922eba774bd1c20
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2298295Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Cr-Original-Commit-Position: refs/branch-heads/4195@{#4}
Cr-Original-Branched-From: 1d94de40-refs/heads/master@{#785504}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2303987
Cr-Commit-Position: refs/heads/master@{#790153}

infra/config/lib/builders.star

@@ -152,13 +152,17 @@ xcode_cache = struct(
 _DEFAULT_BUILDERLESS_OS_CATEGORIES = [os_category.LINUX]
 
 
-def _chromium_tests_property(*, bucketed_triggers):
+def _chromium_tests_property(*, bucketed_triggers, project_trigger_overrides):
   chromium_tests = {}
 
   bucketed_triggers = defaults.get_value('bucketed_triggers', bucketed_triggers)
   if bucketed_triggers:
     chromium_tests['bucketed_triggers'] = True
 
+  project_trigger_overrides = defaults.get_value('project_trigger_overrides', project_trigger_overrides)
+  if project_trigger_overrides:
+    chromium_tests['project_trigger_overrides'] = project_trigger_overrides
+
   return chromium_tests or None
 
 
@@ -246,6 +250,7 @@ defaults = args.defaults(
     goma_use_luci_auth = None,
     mastername = None,
     os = None,
+    project_trigger_overrides = None,
     pool = None,
     ssd = args.COMPUTE,
     use_clang_coverage = False,
@@ -279,6 +284,7 @@ def builder(
     pool=args.DEFAULT,
     ssd=args.DEFAULT,
     bucketed_triggers=args.DEFAULT,
+    project_trigger_overrides=args.DEFAULT,
     configure_kitchen=args.DEFAULT,
     goma_backend=args.DEFAULT,
     goma_debug=args.DEFAULT,
@@ -341,6 +347,11 @@ def builder(
       builder being defined should have the bucket prepended to the builder name
       to trigger. If True, the 'bucketed_triggers' field will be set in the
       '$build/chromium_tests' property. By default, considered False.
+    * project_trigger_overrides - a dict mapping the LUCI projects declared in
+      recipe BotSpecs to the LUCI project to use when triggering builders. When
+      this builder triggers another builder, if the BotSpec for that builder has
+      a LUCI project that is a key in this mapping, the corresponding value will
+      be used instead.
     * configure_kitchen - a boolean indicating whether to configure kitchen. If
       True, emits a property to set the 'git_auth' and 'devshell' fields of the
       '$kitchen' property. By default, considered False.
@@ -446,6 +457,7 @@ def builder(
 
   chromium_tests = _chromium_tests_property(
       bucketed_triggers = bucketed_triggers,
+      project_trigger_overrides = project_trigger_overrides,
   )
   if chromium_tests != None:
     properties['$build/chromium_tests'] = chromium_tests

infra/config/lib/ci.star

@@ -15,6 +15,7 @@ to set the default value. Can also be accessed through `ci.defaults`.
 load('@stdlib//internal/graph.star', 'graph')
 load('@stdlib//internal/luci/common.star', 'keys')
 
+load('//project.star', 'settings')
 load('./builders.star', 'builders')
 load('./args.star', 'args')
 
@@ -101,6 +102,7 @@ def set_defaults(milestone_vars, **kwargs):
       header = '//chromium-header.textpb',
       os = builders.os.LINUX_DEFAULT,
       pool = 'luci.chromium.ci',
+      project_trigger_overrides = {'chromium': settings.project} if not settings.is_master else None,
       repo = 'https://chromium.googlesource.com/chromium/src',
       service_account = 'chromium-ci-builder@chops-service-accounts.iam.gserviceaccount.com',
       swarming_tags = ['vpython:native-python-wrapper'],

infra/config/main.star

@@ -6,7 +6,7 @@
 # See https://chromium.googlesource.com/infra/luci/luci-go/+/HEAD/lucicfg/doc/README.md
 # for information on starlark/lucicfg
 
-load('//project.star', 'master_only_exec')
+load('//project.star', 'master_only_exec', 'settings')
 
 lucicfg.check_version(
     min = '1.15.1',
@@ -45,7 +45,7 @@ lucicfg.emit(
 )
 
 luci.project(
-    name = 'chromium',
+    name = settings.project,
     buildbucket = 'cr-buildbucket.appspot.com',
     logdog = 'luci-logdog.appspot.com',
     milo = 'luci-milo.appspot.com',

infra/config/project.star

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 settings = struct(
+    project = 'chromium',
     # Switch this to False for branches
     is_master = True,
     ref = 'refs/heads/master',