[recipes] Mostly remove bot_update patch_ref hack

We need to do some refactoring to remove the repository hack for
cross-repo tryjobs.

Bug: skia:6473
Change-Id: Ie96fba75f6f1752575a4c7cc5b0208a37f0bd73d
Reviewed-on: https://skia-review.googlesource.com/125724
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Eric Boren <borenet@google.com>

infra/bots/gen_tasks.go

@@ -225,6 +225,7 @@ func kitchenTask(name, recipe, isolate, serviceAccount string, dimensions []stri
 		"buildbucket_build_id": specs.PLACEHOLDER_BUILDBUCKET_BUILD_ID,
 		"buildername":          name,
 		"patch_issue":          specs.PLACEHOLDER_ISSUE,
+		"patch_ref":            specs.PLACEHOLDER_PATCH_REF,
 		"patch_repo":           specs.PLACEHOLDER_PATCH_REPO,
 		"patch_set":            specs.PLACEHOLDER_PATCHSET,
 		"patch_storage":        specs.PLACEHOLDER_PATCH_STORAGE,
@@ -1098,7 +1099,7 @@ func presubmit(b *specs.TasksCfgBuilder, name string) string {
 		"category":         "cq",
 		"patch_gerrit_url": "https://skia-review.googlesource.com",
 		"patch_project":    "skia",
-		"patch_ref":        fmt.Sprintf("refs/changes/%s/%s/%s", specs.PLACEHOLDER_ISSUE_SHORT, specs.PLACEHOLDER_ISSUE, specs.PLACEHOLDER_PATCHSET),
+		"patch_ref":        specs.PLACEHOLDER_PATCH_REF,
 		"reason":           "CQ",
 		"repo_name":        "skia",
 	}

infra/bots/recipe_modules/core/api.py

@@ -142,11 +142,13 @@ class SkiaApi(recipe_api.RecipeApi):
       chromium.revision = 'origin/lkcr'
 
     # Run bot_update.
-
-    # Hack the patch ref if necessary.
-    if self.m.bot_update._issue and self.m.bot_update._patchset:
-      self.m.bot_update._gerrit_ref = self.patch_ref(
-          str(self.m.bot_update._issue), str(self.m.bot_update._patchset))
+    if patch_repo != self.m.properties['repository']:
+      # TODO(borenet): bot_update uses the 'repository' property to determine
+      # which repo the patch should come from. This conflicts with our usage of
+      # the same property to determine which root repo to check out, which may
+      # not be the same as the repository the patch comes from, for which we use
+      # the patch_repo property. Remove this hack by refactoring our checkout
+      # code and properties to agree with bot_update.
       self.m.bot_update._repository = patch_repo
 
     if not self.m.vars.is_trybot and is_parent_revision: