Add test for double defined flags

src/cmds/restic/flags_test.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"testing"
+)
+
+// TestFlags checks for double defined flags, the commands will panic on
+// ParseFlags() when a shorthand flag is defined twice.
+func TestFlags(t *testing.T) {
+	type FlagParser interface {
+		ParseFlags([]string) error
+	}
+
+	for _, cmd := range cmdRoot.Commands() {
+		t.Run(cmd.Name(), func(t *testing.T) {
+			err := cmd.ParseFlags([]string{"--help"})
+			if err.Error() == "pflag: help requested" {
+				err = nil
+			}
+
+			if err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}