cmd/go: support -help

src/cmd/go/main.go

@@ -109,12 +109,22 @@ func main() {
 	if !cmdIsGoTelemetryOff {
 		telemetry.MaybeParent() // Run the upload process. Opening the counter file is idempotent.
 	}
+	// Add global -help flag support
+	var globalHelp bool
+	flag.BoolVar(&globalHelp, "help", false, "show help")
 	flag.Usage = base.Usage
 	flag.Parse()
 	counter.Inc("go/invocations")
 	counter.CountFlags("go/flag:", *flag.CommandLine)
 
 	args := flag.Args()
+
+	// Handle global -help flag
+	if globalHelp {
+		help.Help(os.Stdout, nil)
+		return
+	}
+
 	if len(args) < 1 {
 		base.Usage()
 	}
@@ -310,12 +320,33 @@ func invoke(cmd *base.Command, args []string) {
 		}
 	}
 
-	cmd.Flag.Usage = func() { cmd.Usage() }
+	// Add -help flag support to all commands
+	var helpFlag bool
+	if !cmd.CustomFlags {
+		cmd.Flag.BoolVar(&helpFlag, "help", false, "show help")
+	}
+
+	cmd.Flag.Usage = func() {
+		if helpFlag {
+			// Show full help like "go help <command>"
+			help.Help(os.Stdout, strings.Fields(cmd.LongName()))
+			base.Exit()
+		} else {
+			cmd.Usage()
+		}
+	}
 	if cmd.CustomFlags {
 		args = args[1:]
 	} else {
 		base.SetFromGOFLAGS(&cmd.Flag)
 		cmd.Flag.Parse(args[1:])
+
+		// Check if -help flag was set and show full help
+		if helpFlag {
+			help.Help(os.Stdout, strings.Fields(cmd.LongName()))
+			base.Exit()
+		}
+
 		flagCounterPrefix := "go/" + strings.ReplaceAll(cfg.CmdName, " ", "-") + "/flag"
 		counter.CountFlags(flagCounterPrefix+":", cmd.Flag)
 		counter.CountFlagValue(flagCounterPrefix+"/", cmd.Flag, "buildmode")

src/cmd/go/testdata/script/help_flag.txt

@@ -0,0 +1,62 @@
+# Test that -help flag works for go commands
+
+# go -help shows main help (not an error)
+go -help
+stdout 'Go is a tool for managing Go source code'
+stdout 'Usage:'
+stdout 'go <command> \[arguments\]'
+
+# go build -help shows full help
+go build -help
+stdout 'usage: go build'
+stdout 'Build compiles the packages'
+stdout 'For more about specifying packages'
+
+# go install -help shows full help  
+go install -help
+stdout 'usage: go install'
+stdout 'Install compiles and installs'
+stdout 'For more about specifying packages'
+
+# go get -help shows full help
+go get -help
+stdout 'usage: go get'
+stdout 'Get resolves its command-line arguments'
+stdout 'See also: go build, go install'
+
+# go fmt -help shows full help
+go fmt -help
+stdout 'usage: go fmt'
+stdout 'Fmt runs the command'
+stdout 'See also: go fix, go vet'
+
+# go run -help shows full help
+go run -help
+stdout 'usage: go run'
+stdout 'Run compiles and runs'
+stdout 'See also: go build'
+
+# go run program.go -help should pass -help to the program, not show go run help
+go run helpprog.go -help
+stdout 'Program help message'
+stdout 'Arguments: \[.*helpprog.*-help\]'
+
+-- helpprog.go --
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+)
+
+func main() {
+	var help = flag.Bool("help", false, "show help")
+	flag.Parse()
+
+	fmt.Printf("Arguments: %v\n", os.Args)
+
+	if *help {
+		fmt.Println("Program help message")
+	}
+}