Categories as slice, not a map anymore, order is always preserved

category.go

@@ -0,0 +1,30 @@
+package cli
+
+type CommandCategories []*CommandCategory
+
+type CommandCategory struct {
+	Name     string
+	Commands Commands
+}
+
+func (c CommandCategories) Less(i, j int) bool {
+	return c[i].Name < c[j].Name
+}
+
+func (c CommandCategories) Len() int {
+	return len(c)
+}
+
+func (c CommandCategories) Swap(i, j int) {
+	c[i], c[j] = c[j], c[i]
+}
+
+func (c CommandCategories) AddCommand(category string, command Command) CommandCategories {
+	for _, commandCategory := range c {
+		if commandCategory.Name == category {
+			commandCategory.Commands = append(commandCategory.Commands, command)
+			return c
+		}
+	}
+	return append(c, &CommandCategory{Name: category, Commands: []Command{command}})
+}