Add default values to usage

Check if the value isn't it's zero value and if not add a default value
to the usage text.

1 files changed, 7 insertions, 1 deletions

diff --git a/usage.go b/usage.go
index 9404015..64ed901 100644
--- a/usage.go
+++ b/usage.go
@@ -76,7 +76,6 @@ func (p *Parser) WriteHelp(w io.Writer) {
 		}
 	}
 
-	// write the list of options
 	fmt.Fprint(w, "\noptions:\n")
 	for _, spec := range options {
 		printOption(w, spec)
@@ -101,6 +100,13 @@ func printOption(w io.Writer, spec *spec) {
 		}
 		fmt.Fprint(w, spec.help)
 	}
+	// Check if spec.dest is zero value or not
+	// If it isn't a default value have been added
+	v := spec.dest
+	z := reflect.Zero(v.Type())
+	if v.Interface() != z.Interface() {
+		fmt.Fprintf(w, " [default: %v]", v)
+	}
 	fmt.Fprint(w, "\n")
 }