feat: show environment variables where from values are taken and better usage information.

cmd/test/main.go

@@ -59,10 +59,8 @@ var (
 		),
 	).Desc(
 		"the testing program to show how to use the lib",
-	).Ldesc(
-		"this is the long description where you " +
-			"can put anything you want about the program",
-	)
+	).Ldesc(`This is the long description where you
+can put anything you want about the program.`)
 )
 
 func main() {

mtool/main.go

@@ -15,6 +15,7 @@ type Flags struct {
 	tool *Tool
 	args []string
 	parsedArgs []string
+	envNameMap map[string] []string
 	envMap map[string]string
 }
 
@@ -34,6 +35,7 @@ func (flags *Flags) setEnv(
 	name string,
 	env []string,
 ) bool {
+	flags.envNameMap[name] = env
 	for _, k := range env {
 		value, has := os.LookupEnv(k)
 		if !has {
@@ -47,6 +49,8 @@ func (flags *Flags) setEnv(
 	return false
 }
 
+// Set new string variable
+// to parse.
 func (flags *Flags) StringVar(
 	p *string,
 	name string,
@@ -58,6 +62,7 @@ func (flags *Flags) StringVar(
 	flags.setEnv(name, env)
 }
 
+// Set new int variable to parse.
 func (flags *Flags) IntVar(
 	p *int,
 	name string,
@@ -69,6 +74,7 @@ func (flags *Flags) IntVar(
 	flags.setEnv(name, env)
 }
 
+// Set new int64 variable to parse.
 func (flags *Flags) Int64Var(
 	p *int64,
 	name string,
@@ -80,6 +86,7 @@ func (flags *Flags) Int64Var(
 	flags.setEnv(name, env)
 }
 
+// Set new bool variable to parse.
 func (flags *Flags) BoolVar(
 	p *bool,
 	name string,
@@ -91,6 +98,7 @@ func (flags *Flags) BoolVar(
 	flags.setEnv(name, env)
 }
 
+// Set new float64 variable to parse.
 func (flags *Flags) Float64Var(
 	p *float64,
 	name string,
@@ -102,6 +110,7 @@ func (flags *Flags) Float64Var(
 	flags.setEnv(name, env)
 }
 
+// Set new duration variable to parse.
 func (flags *Flags) DurationVar(
 	p *time.Duration,
 	name string,
@@ -126,14 +135,18 @@ func (flags *Flags) Parse() []string {
 	return flags.parsedArgs
 }
 
+// Get all the arguments, including the
+// parsed ones.
 func (flags *Flags) AllArgs() []string {
 	return flags.args
 }
 
+// Get all the arguments going after options.
 func (flags *Flags) Args() []string {
 	return flags.parsedArgs
 }
 
+// Get the tool currently called.
 func (flags *Flags) Tool() *Tool {
 	return flags.tool
 }

mtool/tool.go

@@ -2,6 +2,7 @@ package mtool
 
 import (
 	"text/tabwriter"
+	"strings"
 	"flag"
 	"sort"
 	"fmt"
@@ -118,14 +119,28 @@ func (t *Tool) Run(args []string) {
 	flags := &Flags{
 		FlagSet : flagSet,
 		envMap: make(map[string]string),
+		envNameMap: make(map[string] []string),
 	}
 	out := flags.Output()
 	flags.Usage = func() {
-		n := 0
+		nflags := 0
 		flags.VisitAll(func(f *flag.Flag){
-			n++
+			nflags++
+			varNames, ok := flags.envNameMap[f.Name]
+			if !ok || len(varNames) == 0 {
+				return
+			}
+
+			f.Usage += " ("
+			for i, name := range varNames {
+				f.Usage += "$"+name
+				if i < len(varNames) - 1 {
+					f.Usage += ", "
+				}
+			}
+			f.Usage += ")"
 		})
-		hasOptions := n != 0
+		hasOptions := nflags != 0
 
 		// Name
 		if usageTool.desc != "" {
@@ -162,6 +177,7 @@ func (t *Tool) Run(args []string) {
 		// Options
 		if hasOptions {
 			fmt.Fprintln(out, "\nOptions:")
+			fmt.Fprintln(out, "  --\n  option terminator")
 			flags.PrintDefaults()
 		}
 		
@@ -178,7 +194,18 @@ func (t *Tool) Run(args []string) {
 
 	// Print available sub commands if
 	// got no arguments.
-	if len(args) == 0 {
+	if len(args) == 0 || func() bool {
+		toolName := args[0]
+		_, ok := t.subs[toolName]
+		if ok {
+			return false
+		}
+		if toolName != "" && toolName[0]=='-' {
+			return true
+		}
+		return false
+	}() {
+
 
 		if t.desc != "" {
 			fmt.Fprintf(
@@ -191,7 +218,11 @@ func (t *Tool) Run(args []string) {
 			"  %s <command>\n", t.FullName())
 
 		if t.ldesc != "" {
-			fmt.Fprintf(out, "\nDescription:\n  %s\n", t.ldesc)
+			fmt.Fprintf(
+				out,
+				"\nDescription:\n  %s\n",
+				t.GetLongFormattedDesc(),
+			)
 		}
 
 		if len(t.subs) > 0 {
@@ -205,7 +236,13 @@ func (t *Tool) Run(args []string) {
 	args = args[1:]
 	
 	if _, ok := t.subs[toolName] ; !ok {
-		fmt.Printf("%s: No such util %q'\n", t.ProgName(), toolName)
+		fmt.Fprintf(
+			out,
+			"%s: No such util %q'\n" +
+			"use ' %s ' to see available commands\n",
+			t.FullName(), toolName,
+			t.FullName(),
+		)
 		os.Exit(1)
 	}
 
@@ -213,3 +250,8 @@ func (t *Tool) Run(args []string) {
 	usageTool = sub
 	sub.Run(args)
 }
+
+func (t *Tool) GetLongFormattedDesc() string {
+	return strings.ReplaceAll(t.ldesc, "\n", "\n  ")
+}
+