New static configuration loading system.

Co-authored-by: Mathieu Lonjaret <mathieu.lonjaret@gmail.com>

pkg/cli/help.go

@@ -0,0 +1,89 @@
+package cli
+
+import (
+	"io"
+	"strings"
+	"text/tabwriter"
+	"text/template"
+
+	"github.com/Masterminds/sprig"
+	"github.com/containous/traefik/pkg/config/flag"
+	"github.com/containous/traefik/pkg/config/generator"
+	"github.com/containous/traefik/pkg/config/parser"
+)
+
+const tmplHelp = `{{ .Cmd.Name }}	{{ .Cmd.Description }}
+
+Usage: {{ .Cmd.Name }} [command] [flags] [arguments]
+
+Use "{{ .Cmd.Name }} [command] --help" for help on any command.
+{{if .SubCommands }}
+Commands:
+{{- range $i, $subCmd := .SubCommands }}
+{{ if not $subCmd.Hidden }}	{{ $subCmd.Name }}	{{ $subCmd.Description }}{{end}}{{end}}
+{{end}}
+{{- if .Flags }}
+Flag's usage: {{ .Cmd.Name }} [--flag=flag_argument] [-f [flag_argument]]	# set flag_argument to flag(s)
+          or: {{ .Cmd.Name }} [--flag[=true|false| ]] [-f [true|false| ]]	# set true/false to boolean flag(s)
+
+Flags:
+{{- range $i, $flag := .Flags }}
+	--{{ SliceIndexN $flag.Name }}  {{if ne $flag.Name "global.sendanonymoususage"}}(Default: "{{ $flag.Default}}"){{end}}
+{{if $flag.Description }}		{{ wrapWith 80 "\n\t\t" $flag.Description }}
+{{else}}
+{{- end}}
+{{- end}}
+{{- end}}
+`
+
+func isHelp(args []string) bool {
+	for _, name := range args {
+		if name == "--help" || name == "-help" || name == "-h" {
+			return true
+		}
+	}
+	return false
+}
+
+// PrintHelp prints the help for the command given as argument.
+func PrintHelp(w io.Writer, cmd *Command) error {
+	var flags []parser.Flat
+	if cmd.Configuration != nil {
+		generator.Generate(cmd.Configuration)
+
+		var err error
+		flags, err = flag.Encode(cmd.Configuration)
+		if err != nil {
+			return err
+		}
+	}
+
+	model := map[string]interface{}{
+		"Cmd":         cmd,
+		"Flags":       flags,
+		"SubCommands": cmd.subCommands,
+	}
+
+	funcs := sprig.TxtFuncMap()
+	funcs["SliceIndexN"] = sliceIndexN
+
+	tmpl, err := template.New("flags").
+		Funcs(funcs).
+		Parse(tmplHelp)
+	if err != nil {
+		return err
+	}
+
+	tw := tabwriter.NewWriter(w, 4, 0, 4, ' ', 0)
+
+	err = tmpl.Execute(tw, model)
+	if err != nil {
+		return err
+	}
+
+	return tw.Flush()
+}
+
+func sliceIndexN(flag string) string {
+	return strings.ReplaceAll(flag, "[0]", "[n]")
+}