flag: include flag name in redefinition panic.

R=golang-dev, rsc, r
CC=golang-dev
https://golang.org/cl/6250043

diff --git a/src/pkg/flag/flag.go b/src/pkg/flag/flag.go
index f0842a18a295d8690cf6588cc6743c429422eb49..5444ad141c5905aedc97c824e2ff6d37ad7e1280 100644 (file)
--- a/src/pkg/flag/flag.go
+++ b/src/pkg/flag/flag.go
@@ -620,8 +620,9 @@ func (f *FlagSet) Var(value Value, name string, usage string) {
        flag := &Flag{name, usage, value, value.String()}
        _, alreadythere := f.formal[name]
        if alreadythere {
-               fmt.Fprintf(f.out(), "%s flag redefined: %s\n", f.name, name)
-               panic("flag redefinition") // Happens only if flags are declared with identical names
+               msg := fmt.Sprintf("%s flag redefined: %s", f.name, name)
+               fmt.Fprintln(f.out(), msg)
+               panic(msg) // Happens only if flags are declared with identical names
        }
        if f.formal == nil {
                f.formal = make(map[string]*Flag)