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

app.go

@@ -6,6 +6,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path"
+	"sort"
 	"time"
 )
 
@@ -37,7 +38,7 @@ type App struct {
 	// Display commands by category
 	CategorizedHelp bool
 	// Populate when displaying AppHelp
-	Categories map[string]Commands
+	Categories CommandCategories
 	// An action to execute when the bash-completion flag is set
 	BashComplete func(context *Context)
 	// An action to execute before any subcommands are run, but after the context is ready
@@ -100,11 +101,12 @@ func (a *App) Run(arguments []string) (err error) {
 	}
 
 	if a.CategorizedHelp {
-		a.Categories = make(map[string]Commands)
+		a.Categories = CommandCategories{}
 		for _, command := range a.Commands {
-			a.Categories[command.Category] = append(a.Categories[command.Category], command)
+			a.Categories = a.Categories.AddCommand(command.Category, command)
 		}
 	}
+	sort.Sort(a.Categories)
 
 	newCmds := []Command{}
 	for _, c := range a.Commands {

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}})
+}

help.go

@@ -23,8 +23,8 @@ VERSION:
 AUTHOR(S):
    {{range .Authors}}{{ . }}{{end}}
    {{end}}{{if .Commands}}
-COMMANDS:{{if .CategorizedHelp}}{{range $category, $commands := .Categories}}{{if $category}}
+COMMANDS:{{if .CategorizedHelp}}{{range .Categories}}{{if .Name}}
-  {{$category}}{{ ":" }}{{end}}{{range $commands}}
+  {{.Name}}{{ ":" }}{{end}}{{range .Commands}}
     {{.Name}}{{with .ShortName}}, {{.}}{{end}}{{ "\t" }}{{.Usage}}{{end}}
 {{end}}{{else}}{{range .Commands}}
    {{.Name}}{{with .ShortName}}, {{.}}{{end}}{{ "\t" }}{{.Usage}}{{end}}