cmd/go: use strings.Builder

Change-Id: I0db93b7bdcd622ce9e23df183de4737744e6d6ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/428294
Reviewed-by: Jenny Rakoczy <jenny@golang.org>
Auto-Submit: Jenny Rakoczy <jenny@golang.org>
Run-TryBot: xie cui <523516579@qq.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Jenny Rakoczy <jenny@golang.org>

src/cmd/go/go_test.go

@@ -1421,7 +1421,7 @@ func TestLdFlagsLongArgumentsIssue42295(t *testing.T) {
 			print(extern)
 		}`)
 	testStr := "test test test test test \n\\ "
-	var buf bytes.Buffer
+	var buf strings.Builder
 	for buf.Len() < sys.ExecArgLengthLimit+1 {
 		buf.WriteString(testStr)
 	}

src/cmd/go/internal/bug/bug.go

@@ -45,7 +45,7 @@ func runBug(ctx context.Context, cmd *base.Command, args []string) {
 	}
 	work.BuildInit()
 
-	var buf bytes.Buffer
+	var buf strings.Builder
 	buf.WriteString(bugHeader)
 	printGoVersion(&buf)
 	buf.WriteString("### Does this issue reproduce with the latest release?\n\n\n")

src/cmd/go/internal/help/help.go

@@ -7,7 +7,6 @@ package help
 
 import (
 	"bufio"
-	"bytes"
 	"fmt"
 	"io"
 	"os"
@@ -31,7 +30,7 @@ func Help(w io.Writer, args []string) {
 		fmt.Fprintln(w, "// Code generated by mkalldocs.sh; DO NOT EDIT.")
 		fmt.Fprintln(w, "// Edit the documentation in other files and rerun mkalldocs.sh to generate this one.")
 		fmt.Fprintln(w)
-		buf := new(bytes.Buffer)
+		buf := new(strings.Builder)
 		PrintUsage(buf, base.Go)
 		usage := &base.Command{Long: buf.String()}
 		cmds := []*base.Command{usage}

src/cmd/go/internal/modload/load.go

@@ -94,7 +94,6 @@ package modload
 // if those packages are not found in existing dependencies of the main module.
 
 import (
-	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -2152,7 +2151,7 @@ func (pkg *loadPkg) stackText() string {
 		stack = append(stack, p)
 	}
 
-	var buf bytes.Buffer
+	var buf strings.Builder
 	for i := len(stack) - 1; i >= 0; i-- {
 		p := stack[i]
 		fmt.Fprint(&buf, p.path)

src/cmd/go/internal/work/build_test.go

@@ -5,7 +5,6 @@
 package work
 
 import (
-	"bytes"
 	"fmt"
 	"io/fs"
 	"os"
@@ -233,7 +232,7 @@ func TestRespectSetgidDir(t *testing.T) {
 	// Check that `cp` is called instead of `mv` by looking at the output
 	// of `(*Builder).ShowCmd` afterwards as a sanity check.
 	cfg.BuildX = true
-	var cmdBuf bytes.Buffer
+	var cmdBuf strings.Builder
 	b.Print = func(a ...any) (int, error) {
 		return cmdBuf.WriteString(fmt.Sprint(a...))
 	}

src/cmd/go/internal/work/buildid.go

@@ -160,12 +160,12 @@ func (b *Builder) toolID(name string) string {
 
 	cmdline := str.StringList(cfg.BuildToolexec, path, "-V=full")
 	cmd := exec.Command(cmdline[0], cmdline[1:]...)
-	var stdout, stderr bytes.Buffer
+	var stdout, stderr strings.Builder
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
 	if err := cmd.Run(); err != nil {
 		if stderr.Len() > 0 {
-			os.Stderr.Write(stderr.Bytes())
+			os.Stderr.WriteString(stderr.String())
 		}
 		base.Fatalf("go: error obtaining buildID for %s: %v", desc, err)
 	}

src/cmd/go/internal/work/exec.go

@@ -2159,7 +2159,7 @@ func (b *Builder) runOut(a *Action, dir string, env []string, cmdargs ...any) ([
 // output unambiguous.
 // TODO: See issue 5279. The printing of commands needs a complete redo.
 func joinUnambiguously(a []string) string {
-	var buf bytes.Buffer
+	var buf strings.Builder
 	for i, s := range a {
 		if i > 0 {
 			buf.WriteByte(' ')