src/cmd/relnote, doc/next: add release note check

Add a test that every file in api/next has corresponding
release note fragments.

Vendor in golang.org/x/build/relnote, which brings along some other
things.

Modify dist/test.go to configure the test to run on some trybots.

For #64169.

Change-Id: If87d11350ea6b2605bc3ab31c491fa28f1d6ee7d
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/go/+/556995
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

1 files changed, 39 insertions, 0 deletions

diff --git a/src/cmd/relnote/relnote_test.go b/src/cmd/relnote/relnote_test.go
new file mode 100644
index 0000000000..ba3a059704
--- /dev/null
+++ b/src/cmd/relnote/relnote_test.go
@@ -0,0 +1,39 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"flag"
+	"internal/testenv"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"golang.org/x/build/relnote"
+)
+
+var flagCheck = flag.Bool("check", false, "run API release note checks")
+
+// Check that each file in api/next has corresponding release note files in doc/next.
+func TestCheckAPIFragments(t *testing.T) {
+	if !*flagCheck {
+		t.Skip("-check not specified")
+	}
+	root := testenv.GOROOT(t)
+	rootFS := os.DirFS(root)
+	files, err := fs.Glob(rootFS, "api/next/*.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("checking release notes for %d files in api/next", len(files))
+	docFS := os.DirFS(filepath.Join(root, "doc", "next"))
+	// Check that each api/next file has a corresponding release note fragment.
+	for _, apiFile := range files {
+		if err := relnote.CheckAPIFile(rootFS, apiFile, docFS); err != nil {
+			t.Errorf("%s: %v", apiFile, err)
+		}
+	}
+}