support go --help

Author: juanrgon

src/cmd/go/main.go

@@ -109,12 +109,23 @@ 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()
 	}

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

@@ -1,5 +1,11 @@
 # 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'