cmd/geth: reorganise help section for new cli flag handling

cmd/geth/usage.go

@@ -20,6 +20,7 @@ package main
 
 import (
 	"io"
+	"sort"
 
 	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/internal/debug"
@@ -189,6 +190,39 @@ var AppHelpFlagGroups = []flagGroup{
 	},
 }
 
+// byCategory sorts an array of flagGroup by Name in the order
+// defined in AppHelpFlagGroups.
+type byCategory []flagGroup
+
+func (a byCategory) Len() int      { return len(a) }
+func (a byCategory) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
+func (a byCategory) Less(i, j int) bool {
+	iCat, jCat := a[i].Name, a[j].Name
+	iIdx, jIdx := len(AppHelpFlagGroups), len(AppHelpFlagGroups) // ensure non categorized flags come last
+
+	for i, group := range AppHelpFlagGroups {
+		if iCat == group.Name {
+			iIdx = i
+		}
+		if jCat == group.Name {
+			jIdx = i
+		}
+	}
+
+	return iIdx < jIdx
+}
+
+func flagCategory(flag cli.Flag) string {
+	for _, category := range AppHelpFlagGroups {
+		for _, flg := range category.Flags {
+			if flg.GetName() == flag.GetName() {
+				return category.Name
+			}
+		}
+	}
+	return "MISC"
+}
+
 func init() {
 	// Override the default app help template
 	cli.AppHelpTemplate = AppHelpTemplate
@@ -198,6 +232,7 @@ func init() {
 		App        interface{}
 		FlagGroups []flagGroup
 	}
+
 	// Override the default app help printer, but only for the global app help
 	originalHelpPrinter := cli.HelpPrinter
 	cli.HelpPrinter = func(w io.Writer, tmpl string, data interface{}) {
@@ -227,6 +262,27 @@ func init() {
 			}
 			// Render out custom usage screen
 			originalHelpPrinter(w, tmpl, helpData{data, AppHelpFlagGroups})
+		} else if tmpl == utils.CommandHelpTemplate {
+			// Iterate over all command specific flags and categorize them
+			categorized := make(map[string][]cli.Flag)
+			for _, flag := range data.(cli.Command).Flags {
+				if _, ok := categorized[flag.String()]; !ok {
+					categorized[flagCategory(flag)] = append(categorized[flagCategory(flag)], flag)
+				}
+			}
+
+			// sort to get a stable ordering
+			sorted := make([]flagGroup, 0, len(categorized))
+			for cat, flgs := range categorized {
+				sorted = append(sorted, flagGroup{cat, flgs})
+			}
+			sort.Sort(byCategory(sorted))
+
+			// add sorted array to data and render with default printer
+			originalHelpPrinter(w, tmpl, map[string]interface{}{
+				"cmd":              data,
+				"categorizedFlags": sorted,
+			})
 		} else {
 			originalHelpPrinter(w, tmpl, data)
 		}