internal/task: clean up tagging commit selection logic

Clean up after the change to read the branch head later. Also fix a bug:
in the version tasks, we want to know exactly what commit we're tagging,
so we pass in the expected commit, and AwaitCL returns that if no CL was
necessary. But here we want to tag the latest branch head if there's no
CL necessary. So we need a different Await function.

For golang/go#48523.

Change-Id: I97f92b22d4f29edeb52d06c311fddaa6596da0c2
Reviewed-on: https://go-review.googlesource.com/c/build/+/444116
Reviewed-by: Dmitri Shuralyov <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Heschi Kreinick <[email protected]>
Run-TryBot: Heschi Kreinick <[email protected]>

Author: heschi

Diff for: internal/task/tagx.go

@@ -253,15 +253,15 @@ func (x *TagXReposTasks) planRepo(wd *wf.Definition, repo TagRepo, updated map[s
 	wd = wd.Sub(repo.Name)
 	repoName, branch := wf.Const(repo.Name), wf.Const("master")
 
-	head := wf.Task2(wd, "read branch head", x.Gerrit.ReadBranchHead, repoName, branch)
-	tagCandidate := head
-	if len(deps) != 0 {
-		gomod := wf.Task3(wd, "generate updated go.mod", x.UpdateGoMod, wf.Const(repo), wf.Slice(deps...), head)
+	var tagCommit wf.Value[string]
+	if len(deps) == 0 {
+		tagCommit = wf.Task2(wd, "read branch head", x.Gerrit.ReadBranchHead, repoName, branch)
+	} else {
+		gomod := wf.Task3(wd, "generate updated go.mod", x.UpdateGoMod, wf.Const(repo), wf.Slice(deps...), branch)
 		cl := wf.Task2(wd, "mail updated go.mod", x.MailGoMod, repoName, gomod)
-		versionTasks := &VersionTasks{Gerrit: x.Gerrit}
-		tagCandidate = wf.Task2(wd, "wait for submit", versionTasks.AwaitCL, cl, wf.Const(""))
+		tagCommit = wf.Task3(wd, "wait for submit", x.AwaitGoMod, cl, repoName, branch)
 	}
-	greenCommit := wf.Task2(wd, "wait for green post-submit", x.AwaitGreen, wf.Const(repo), tagCandidate)
+	greenCommit := wf.Task2(wd, "wait for green post-submit", x.AwaitGreen, wf.Const(repo), tagCommit)
 	tagged := wf.Task2(wd, "tag if appropriate", x.MaybeTag, wf.Const(repo), greenCommit)
 	return tagged, true
 }
@@ -270,8 +270,8 @@ type UpdatedModSum struct {
 	Mod, Sum string
 }
 
-func (x *TagXReposTasks) UpdateGoMod(ctx *wf.TaskContext, repo TagRepo, deps []TagRepo, _ string) (UpdatedModSum, error) {
-	commit, err := x.Gerrit.ReadBranchHead(ctx, repo.Name, "master")
+func (x *TagXReposTasks) UpdateGoMod(ctx *wf.TaskContext, repo TagRepo, deps []TagRepo, branch string) (UpdatedModSum, error) {
+	commit, err := x.Gerrit.ReadBranchHead(ctx, repo.Name, branch)
 	if err != nil {
 		return UpdatedModSum{}, err
 	}
@@ -391,6 +391,19 @@ will be tagged with its next minor version.
 		"go.sum": gomod.Sum,
 	})
 }
+
+func (x *TagXReposTasks) AwaitGoMod(ctx *wf.TaskContext, changeID, repo, branch string) (string, error) {
+	if changeID == "" {
+		ctx.Printf("No CL was necessary")
+		return x.Gerrit.ReadBranchHead(ctx, repo, branch)
+	}
+
+	ctx.Printf("Awaiting review/submit of %v", ChangeLink(changeID))
+	return AwaitCondition(ctx, 10*time.Second, func() (string, bool, error) {
+		return x.Gerrit.Submitted(ctx, changeID, "")
+	})
+}
+
 func (x *TagXReposTasks) AwaitGreen(ctx *wf.TaskContext, repo TagRepo, commit string) (string, error) {
 	return AwaitCondition(ctx, time.Minute, func() (string, bool, error) {
 		return x.findGreen(ctx, repo, commit, false)