Imported Upstream version 1.1~hg20130304upstream/1.1_hg20130304

1 files changed, 16 insertions, 3 deletions

diff --git a/src/pkg/flag/flag.go b/src/pkg/flag/flag.go
index 5444ad141..85dd8c3b3 100644
--- a/src/pkg/flag/flag.go
+++ b/src/pkg/flag/flag.go
@@ -33,7 +33,7 @@
 
 	After parsing, the arguments after the flag are available as the
 	slice flag.Args() or individually as flag.Arg(i).
-	The arguments are indexed from 0 up to flag.NArg().
+	The arguments are indexed from 0 through flag.NArg()-1.
 
 	Command line flag syntax:
 		-flag
@@ -91,6 +91,15 @@ func (b *boolValue) Set(s string) error {
 
 func (b *boolValue) String() string { return fmt.Sprintf("%v", *b) }
 
+func (b *boolValue) IsBoolFlag() bool { return true }
+
+// optional interface to indicate boolean flags that can be
+// supplied without "=value" text
+type boolFlag interface {
+	Value
+	IsBoolFlag() bool
+}
+
 // -- int Value
 type intValue int
 
@@ -204,6 +213,10 @@ func (d *durationValue) String() string { return (*time.Duration)(d).String() }
 
 // Value is the interface to the dynamic value stored in a flag.
 // (The default value is represented as a string.)
+//
+// If a Value has an IsBoolFlag() bool method returning true,
+// the command-line parser makes -name equivalent to -name=true
+// rather than using the next command-line argument.
 type Value interface {
 	String() string
 	Set(string) error
@@ -704,10 +717,10 @@ func (f *FlagSet) parseOne() (bool, error) {
 		}
 		return false, f.failf("flag provided but not defined: -%s", name)
 	}
-	if fv, ok := flag.Value.(*boolValue); ok { // special case: doesn't need an arg
+	if fv, ok := flag.Value.(boolFlag); ok && fv.IsBoolFlag() { // special case: doesn't need an arg
 		if has_value {
 			if err := fv.Set(value); err != nil {
-				f.failf("invalid boolean value %q for  -%s: %v", value, name, err)
+				return false, f.failf("invalid boolean value %q for  -%s: %v", value, name, err)
 			}
 		} else {
 			fv.Set("true")