Show 'correct' explicit bool value syntax in help

Author: alimpfard

flag.go

@@ -723,9 +723,16 @@ func (f *FlagSet) FlagUsagesWrapped(cols int) string {
 		}
 
 		varname, usage := UnquoteUsage(flag)
-		if varname != "" {
+		if flag.Value.Type() == "bool" {
+			if varname != "" {
+				line += "[=" + varname + "]"
+			} else {
+				line += "[=value]"
+			}
+		} else if varname != "" {
 			line += " " + varname
 		}
+
 		if flag.NoOptDefVal != "" {
 			switch flag.Value.Type() {
 			case "string":

flag_test.go

@@ -1271,9 +1271,9 @@ func TestHiddenFlagUsage(t *testing.T) {
 	}
 }
 
-const defaultOutput = `      --A                         for bootstrapping, allow 'any' type
-      --Alongflagname             disable bounds checking
-  -C, --CCC                       a boolean defaulting to true (default true)
+const defaultOutput = `      --A[=value]                 for bootstrapping, allow 'any' type
+      --Alongflagname[=value]     disable bounds checking
+  -C, --CCC[=value]               a boolean defaulting to true (default true)
       --D path                    set relative path for local imports
   -E, --EEE num[=1234]            a num with NoOptDefVal (default 4321)
       --F number                  a non-zero number (default 2.7)

printusage_test.go

@@ -6,12 +6,12 @@ import (
 	"testing"
 )
 
-const expectedOutput = `      --long-form    Some description
-      --long-form2   Some description
-                       with multiline
-  -s, --long-name    Some description
-  -t, --long-name2   Some description with
-                       multiline
+const expectedOutput = `      --long-form[=value]    Some description
+      --long-form2[=value]   Some description
+                               with multiline
+  -s, --long-name[=value]    Some description
+  -t, --long-name2[=value]   Some description with
+                               multiline
 `
 
 func setUpPFlagSet(buf io.Writer) *FlagSet {
@@ -47,11 +47,11 @@ func setUpPFlagSet2(buf io.Writer) *FlagSet {
 	return f
 }
 
-const expectedOutput2 = `      --long-form                    Some description
-      --long-form2                   Some description
+const expectedOutput2 = `      --long-form[=value]            Some description
+      --long-form2[=value]           Some description
                                        with multiline
-  -s, --long-name                    Some description
-  -t, --long-name2                   Some description with
+  -s, --long-name[=value]            Some description
+  -t, --long-name2[=value]           Some description with
                                        multiline
   -o, --other-very-long-arg string   Some very long description having
                                      break the limit (default