flag: improve docs for PrintDefaults; clarify how to change output destination

The existing docs only mention that it is possible to change the output
destination of PrintDefaults from the default of standard error, but fail to
mention how to actually do so. This change fixes this lack by directing users
to CommandLine.SetOutput.

Fixes #15024

Change-Id: Ieaa7edbebd23d4ea6fa7e53d97a87143d590bdb3
Reviewed-on: https://go-review.googlesource.com/c/145203
Reviewed-by: Rob Pike <r@golang.org>

diff --git a/src/flag/flag.go b/src/flag/flag.go
index 2eef9d6ab9ae2fc945d35719278bdf194f1183b3..c312c62a582157b342552196104d358218f2a536 100644 (file)
--- a/src/flag/flag.go
+++ b/src/flag/flag.go
@@ -548,6 +548,8 @@ func (f *FlagSet) PrintDefaults() {
 // the output will be
 //     -I directory
 //             search directory for include files.
+//
+// To change the destination for flag messages, call CommandLine.SetOutput.
 func PrintDefaults() {
        CommandLine.PrintDefaults()
 }