cmd/coordinator: link to LUCI UI for non-top-level dashboard pages

The build.golang.org dashboard gained support to display build results
from LUCI, in addition to legacy builder results (go.dev/issue/65913),
but only for the default top-level view.

When visiting more detailed pages, like page 2 of commits for the main
Go repo, or detailed views for golang.org/x repos, no LUCI build results
are shown, which can be confusing. So, when displaying LUCI results
(i.e., the 'legacyonly' query parameter isn't used to hide them),
change links to detailed views on the top-level view to point to the
LUCI UI where results can in fact be viewed.

For golang/go#28643.
For golang/go#65913.
For golang/go#70314.

Change-Id: I3ebfba5bc6d0cd2e37d8e5fc1386843c6e298ce7
Reviewed-on: https://go-review.googlesource.com/c/build/+/644156
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

cmd/coordinator/internal/legacydash/ui.go

@@ -551,6 +551,11 @@ func (tb *uiTemplateDataBuilder) buildTemplateData(ctx context.Context, datastor
 		// to do there in the case of LUCI.
 	}
 
+	if tb.showLUCI() {
+		data.Pagination = &Pagination{} // Disable pagination links because they don't have LUCI results now.
+		data.LinkToLUCI = true
+	}
+
 	return data, nil
 }
 
@@ -875,7 +880,7 @@ var osPriority = map[string]int{
 
 // TagState represents the state of all Packages at a branch.
 type TagState struct {
-	Name     string      // Go branch name: "master", "release-branch.go1.4", etc
+	Name     string      // Go branch name: "master", "release-branch.go1.4", etc.
 	Tag      *CommitInfo // current Go commit on the Name branch
 	Packages []*PackageState
 	Builders []string
@@ -890,6 +895,15 @@ func (ts *TagState) Branch() string {
 	return ts.Name
 }
 
+// LUCIBranch returns the short Go branch name as used in LUCI: "tip", "1.24", etc.
+func (ts *TagState) LUCIBranch() string {
+	shortGoBranch := "tip"
+	if after, ok := strings.CutPrefix(ts.Name, "release-branch.go"); ok {
+		shortGoBranch = after
+	}
+	return shortGoBranch
+}
+
 // PackageState represents the state of a Package (x/foo repo) for given Go branch.
 type PackageState struct {
 	Package *Package
@@ -944,6 +958,7 @@ type uiTemplateData struct {
 	Branches   []string
 	Branch     string
 	Repo       string // the repo gerrit project name. "go" if unspecified in the request.
+	LinkToLUCI bool   // whether to display links to LUCI UI
 }
 
 // getActiveBuilds returns the builds that coordinator is currently doing.

cmd/coordinator/internal/legacydash/ui.html

@@ -189,6 +189,7 @@ <h1>
         <a {{if .HasPrev}}href="?{{with $.Package.Path}}repo={{.}}&{{end}}page={{.Prev}}{{with $.Branch}}&branch={{.}}{{end}}"{{else}}class="inactive"{{end}}>newer</a>
         <a {{if .Next}}href="?{{with $.Package.Path}}repo={{.}}&{{end}}page={{.Next}}{{with $.Branch}}&branch={{.}}{{end}}"{{else}}class="inactive"{{end}}>older</a>
         <a {{if .HasPrev}}href=".{{with $.Branch}}?branch={{.}}{{end}}"{{else}}class="inactive"{{end}}>latest</a>
+        {{if $.LinkToLUCI}}<a href="https://ci.chromium.org/p/golang/g/go-gotip/console">more in LUCI UI</a>{{end}}
       </nav>
     </div>
     {{end}}
@@ -200,6 +201,7 @@ <h1>
   {{range $.TagState}}
     {{$goHash := .Tag.Hash}}
     {{$goBranch := .Branch}}
+    {{$goLUCI := .LUCIBranch}}
     {{$builders := .Builders}}
     {{if .Packages}}
       <h2>
@@ -257,7 +259,20 @@ <h2>
       </tr>
     {{range $pkg := .Packages}}
       <tr class="commit">
-        <td><a title="{{.Package.Path}}" href="?repo={{.Package.Path}}">{{.Package.Name}}</a></td>
+        <td>
+          <a title="{{.Package.Path}}"
+            {{if $.LinkToLUCI}}
+              href="https://ci.chromium.org/p/golang/g/x-{{.Package.Name}}-go{{$goLUCI}}/console"
+            {{else}}
+              href="?repo={{.Package.Path}}"
+            {{end}}
+          >{{.Package.Name}}</a>
+          {{if $.LinkToLUCI}}
+            <small>(<a title="View {{.Package.Path}} builds ordered by Go commit."
+              href="https://ci.chromium.org/p/golang/g/x-{{.Package.Name}}-go{{$goLUCI}}-by-go/console"
+            >by go</a>)</small>
+          {{end}}
+        </td>
         <td class="hash">
           {{$h := $pkg.Commit.Hash}}
           <a href="https://go-review.googlesource.com/q/{{$h}}">{{shortHash $h}}</a>