Add word-wrap support based on terminal size

go.mod

@@ -5,5 +5,7 @@ go 1.11
 require (
 	github.com/BurntSushi/toml v0.3.1
 	github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d
+	github.com/mattn/go-runewidth v0.0.8 // indirect
+	github.com/nsf/termbox-go v0.0.0-20191229070316-58d4fcbce2a7
 	gopkg.in/yaml.v2 v2.2.2
 )

go.sum

@@ -2,6 +2,10 @@ github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d h1:U+s90UTSYgptZMwQh2aRr3LuazLJIa+Pg3Kc1ylSYVY=
 github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
+github.com/mattn/go-runewidth v0.0.8 h1:3tS41NlGYSmhhe/8fhGRzc+z3AYCw1Fe1WAyLuujKs0=
+github.com/mattn/go-runewidth v0.0.8/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
+github.com/nsf/termbox-go v0.0.0-20191229070316-58d4fcbce2a7 h1:OkWEy7aQeQTbgdrcGi9bifx+Y6bMM7ae7y42hDFaBvA=
+github.com/nsf/termbox-go v0.0.0-20191229070316-58d4fcbce2a7/go.mod h1:IuKpRQcYE1Tfu+oAQqaLisqDeXgjyyltCfsaoYN18NQ=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/russross/blackfriday/v2 v2.0.1 h1:lPqVAte+HuHNfhJ/0LC98ESWRz8afy9tM/0RK8m9o+Q=

help.go

@@ -8,6 +8,8 @@ import (
 	"text/tabwriter"
 	"text/template"
 	"unicode/utf8"
+
+	"github.com/nsf/termbox-go"
 )
 
 var helpCommand = &Command{
@@ -263,7 +265,9 @@ func ShowCommandCompletions(ctx *Context, command string) {
 // allow using arbitrary functions in template rendering.
 func printHelpCustom(out io.Writer, templ string, data interface{}, customFuncs map[string]interface{}) {
 	funcMap := template.FuncMap{
-		"join": strings.Join,
+		"join":   strings.Join,
+		"wrap":   wrap,
+		"offset": offset,
 	}
 	for key, value := range customFuncs {
 		funcMap[key] = value
@@ -366,3 +370,37 @@ func checkCommandCompletions(c *Context, name string) bool {
 	ShowCommandCompletions(c, name)
 	return true
 }
+
+func wrap(input string, offset int) string {
+	if err := termbox.Init(); err != nil {
+		return input
+	}
+	w, _ := termbox.Size()
+	termbox.Close()
+
+	if w > offset && len(input) > w-offset {
+		lineWidth := w - offset
+		words := strings.Fields(strings.TrimSpace(input))
+		if len(words) == 0 {
+			return input
+		}
+		wrapped := words[0]
+		spaceLeft := lineWidth - len(wrapped)
+		for _, word := range words[1:] {
+			if len(word)+1 > spaceLeft {
+				wrapped += "\n" + strings.Repeat(" ", offset) + word
+				spaceLeft = lineWidth - len(word)
+			} else {
+				wrapped += " " + word
+				spaceLeft -= 1 + len(word)
+			}
+		}
+		return wrapped
+	}
+
+	return input
+}
+
+func offset(input string, fixed int) int {
+	return len(input) + fixed
+}

template.go

@@ -4,7 +4,7 @@ package cli
 // cli.go uses text/template to render templates. You can
 // render custom help text by setting this variable.
 var AppHelpTemplate = `NAME:
-   {{.Name}}{{if .Usage}} - {{.Usage}}{{end}}
+   {{$v := offset .Name 6}}{{wrap .Name 3}}{{if .Usage}} - {{wrap .Usage $v}}{{end}}
 
 USAGE:
    {{if .UsageText}}{{.UsageText}}{{else}}{{.HelpName}} {{if .VisibleFlags}}[global options]{{end}}{{if .Commands}} command [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}{{if .Version}}{{if not .HideVersion}}