cmd/go: add tool -n flag

As in gdb $(go tool -n 6g).

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5689066

diff --git a/src/cmd/go/tool.go b/src/cmd/go/tool.go
index 19b0d37dc001ca11580b18616ed49bf71069d9da..9776d3359e836a4384d84df76187ce564b11432f 100644 (file)
--- a/src/cmd/go/tool.go
+++ b/src/cmd/go/tool.go
@@ -17,12 +17,15 @@ import (
 
 var cmdTool = &Command{
        Run:       runTool,
-       UsageLine: "tool command [args...]",
+       UsageLine: "tool [-n] command [args...]",
        Short:     "run specified go tool",
        Long: `
 Tool runs the go tool command identified by the arguments.
 With no arguments it prints the list of known tools.
 
+The -n flag causes tool to print the command that would be
+executed but not execute it.
+
 For more about each tool command, see 'go tool command -h'.
 `,
 }
@@ -32,8 +35,14 @@ var (
        toolGOARCH    = runtime.GOARCH
        toolIsWindows = toolGOOS == "windows"
        toolDir       = build.ToolDir
+
+       toolN bool
 )
 
+func init() {
+       cmdTool.Flag.BoolVar(&toolN, "n", false, "")
+}
+
 const toolWindowsExtension = ".exe"
 
 func tool(name string) string {
@@ -67,6 +76,11 @@ func runTool(cmd *Command, args []string) {
                setExitStatus(3)
                return
        }
+
+       if toolN {
+               fmt.Printf("%s %s\n", toolPath, strings.Join(args[1:], " "))
+               return
+       }
        toolCmd := &exec.Cmd{
                Path:   toolPath,
                Args:   args,