cmd/go: add internal/note, internal/sumweb, internal/tlog from golang…

….org/x/exp/sumdb

Copied and updated import paths.
Eventually we will probably publish
these packages somewhere in golang.org/x
(as non-internal packages) and then we will
be able to vendor them properly.
For now, copy.

sumweb.globsMatchPath moved to str.GlobsMatchPath.

Change-Id: I4585e6dc5daa423e4ca9669195d41e58e7c8c275
Reviewed-on: https://go-review.googlesource.com/c/go/+/173950
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/internal/note/example_test.go

@@ -0,0 +1,128 @@
+// Copyright 2019 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 note_test
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	"cmd/go/internal/note"
+)
+
+func ExampleSign() {
+	skey := "PRIVATE+KEY+PeterNeumann+c74f20a3+AYEKFALVFGyNhPJEMzD1QIDr+Y7hfZx09iUvxdXHKDFz"
+	text := "If you think cryptography is the answer to your problem,\n" +
+		"then you don't know what your problem is.\n"
+
+	signer, err := note.NewSigner(skey)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	msg, err := note.Sign(&note.Note{Text: text}, signer)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	os.Stdout.Write(msg)
+
+	// Output:
+	// If you think cryptography is the answer to your problem,
+	// then you don't know what your problem is.
+	//
+	// — PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+}
+
+func ExampleOpen() {
+	vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+	msg := []byte("If you think cryptography is the answer to your problem,\n" +
+		"then you don't know what your problem is.\n" +
+		"\n" +
+		"— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+
+	verifier, err := note.NewVerifier(vkey)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	verifiers := note.VerifierList(verifier)
+
+	n, err := note.Open(msg, verifiers)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Printf("%s (%08x):\n%s", n.Sigs[0].Name, n.Sigs[0].Hash, n.Text)
+
+	// Output:
+	// PeterNeumann (c74f20a3):
+	// If you think cryptography is the answer to your problem,
+	// then you don't know what your problem is.
+}
+
+var rand = struct {
+	Reader io.Reader
+}{
+	zeroReader{},
+}
+
+type zeroReader struct{}
+
+func (zeroReader) Read(buf []byte) (int, error) {
+	for i := range buf {
+		buf[i] = 0
+	}
+	return len(buf), nil
+}
+
+func ExampleSign_add_signatures() {
+	vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+	msg := []byte("If you think cryptography is the answer to your problem,\n" +
+		"then you don't know what your problem is.\n" +
+		"\n" +
+		"— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+
+	verifier, err := note.NewVerifier(vkey)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	verifiers := note.VerifierList(verifier)
+
+	n, err := note.Open([]byte(msg), verifiers)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	skey, vkey, err := note.GenerateKey(rand.Reader, "EnochRoot")
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	_ = vkey // give to verifiers
+
+	me, err := note.NewSigner(skey)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	msg, err = note.Sign(n, me)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	os.Stdout.Write(msg)
+
+	// Output:
+	// If you think cryptography is the answer to your problem,
+	// then you don't know what your problem is.
+	//
+	// — PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+	// — EnochRoot rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ=
+}