cmd: Migrate to `spf13/cobra`, remove single-dash arg support (#4565)

* cmd: migrate to spf13/cobra

* add `manpage` command

* limit Caddy tagline to root `help` only

* hard-code the manpage section to 8

4 files changed, 82 insertions, 122 deletions

diff --git a/cmd/cobra.go b/cmd/cobra.go
new file mode 100644
index 000000000..ad95ec0d3
--- /dev/null
+++ b/cmd/cobra.go
@@ -0,0 +1,33 @@
+package caddycmd
+
+import (
+	"github.com/spf13/cobra"
+)
+
+var rootCmd = &cobra.Command{
+	Use: "caddy",
+}
+
+const docsHeader = "{{if not .HasParent}} Caddy is an extensible server platform.\n\n{{end}}"
+const fullDocsFooter = `Full documentation is available at:
+https://caddyserver.com/docs/command-line
+`
+
+func init() {
+	rootCmd.SetHelpTemplate(docsHeader + rootCmd.HelpTemplate() + "\n" + fullDocsFooter)
+}
+
+func caddyCmdToCoral(caddyCmd Command) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   caddyCmd.Name,
+		Short: caddyCmd.Short,
+		Long:  caddyCmd.Long,
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			fls := cmd.Flags()
+			_, err := caddyCmd.Func(Flags{fls})
+			return err
+		},
+	}
+	cmd.Flags().AddGoFlagSet(caddyCmd.Flags)
+	return cmd
+}
diff --git a/cmd/commandfuncs.go b/cmd/commandfuncs.go
index 67015f78d..874cc6ff2 100644
--- a/cmd/commandfuncs.go
+++ b/cmd/commandfuncs.go
@@ -29,7 +29,6 @@ import (
 	"os/exec"
 	"runtime"
 	"runtime/debug"
-	"sort"
 	"strings"
 
 	"github.com/aryann/difflib"
@@ -580,70 +579,6 @@ func cmdFmt(fl Flags) (int, error) {
 	return caddy.ExitCodeSuccess, nil
 }
 
-func cmdHelp(fl Flags) (int, error) {
-	const fullDocs = `Full documentation is available at:
-https://caddyserver.com/docs/command-line`
-
-	args := fl.Args()
-	if len(args) == 0 {
-		s := `Caddy is an extensible server platform.
-
-usage:
-  caddy <command> [<args...>]
-
-commands:
-`
-		keys := make([]string, 0, len(commands))
-		for k := range commands {
-			keys = append(keys, k)
-		}
-		sort.Strings(keys)
-		for _, k := range keys {
-			cmd := commands[k]
-			short := strings.TrimSuffix(cmd.Short, ".")
-			s += fmt.Sprintf("  %-15s %s\n", cmd.Name, short)
-		}
-
-		s += "\nUse 'caddy help <command>' for more information about a command.\n"
-		s += "\n" + fullDocs + "\n"
-
-		fmt.Print(s)
-
-		return caddy.ExitCodeSuccess, nil
-	} else if len(args) > 1 {
-		return caddy.ExitCodeFailedStartup, fmt.Errorf("can only give help with one command")
-	}
-
-	subcommand, ok := commands[args[0]]
-	if !ok {
-		return caddy.ExitCodeFailedStartup, fmt.Errorf("unknown command: %s", args[0])
-	}
-
-	helpText := strings.TrimSpace(subcommand.Long)
-	if helpText == "" {
-		helpText = subcommand.Short
-		if !strings.HasSuffix(helpText, ".") {
-			helpText += "."
-		}
-	}
-
-	result := fmt.Sprintf("%s\n\nusage:\n  caddy %s %s\n",
-		helpText,
-		subcommand.Name,
-		strings.TrimSpace(subcommand.Usage),
-	)
-
-	if help := flagHelp(subcommand.Flags); help != "" {
-		result += fmt.Sprintf("\nflags: (NOTE: prefix flags with `--` instead of `-`)\n%s", help)
-	}
-
-	result += "\n" + fullDocs + "\n"
-
-	fmt.Print(result)
-
-	return caddy.ExitCodeSuccess, nil
-}
-
 // AdminAPIRequest makes an API request according to the CLI flags given,
 // with the given HTTP method and request URI. If body is non-nil, it will
 // be assumed to be Content-Type application/json. The caller should close
diff --git a/cmd/commands.go b/cmd/commands.go
index e454f7b62..2085dfcd0 100644
--- a/cmd/commands.go
+++ b/cmd/commands.go
@@ -16,7 +16,13 @@ package caddycmd
 
 import (
 	"flag"
+	"fmt"
+	"os"
 	"regexp"
+	"strings"
+
+	"github.com/caddyserver/caddy/v2"
+	"github.com/spf13/cobra/doc"
 )
 
 // Command represents a subcommand. Name, Func,
@@ -71,13 +77,6 @@ var commands = make(map[string]Command)
 
 func init() {
 	RegisterCommand(Command{
-		Name:  "help",
-		Func:  cmdHelp,
-		Usage: "<command>",
-		Short: "Shows help for a Caddy subcommand",
-	})
-
-	RegisterCommand(Command{
 		Name:  "start",
 		Func:  cmdStart,
 		Usage: "[--config <path> [--adapter <name>]] [--envfile <path>] [--watch] [--pidfile <file>]",
@@ -346,16 +345,50 @@ EXPERIMENTAL: May be changed or removed.
 		}(),
 	})
 
+	RegisterCommand(Command{
+		Name: "manpage",
+		Func: func(fl Flags) (int, error) {
+			dir := strings.TrimSpace(fl.String("directory"))
+			if dir == "" {
+				return caddy.ExitCodeFailedQuit, fmt.Errorf("designated output directory and specified section are required")
+			}
+			if err := os.MkdirAll(dir, 0755); err != nil {
+				return caddy.ExitCodeFailedQuit, err
+			}
+			if err := doc.GenManTree(rootCmd, &doc.GenManHeader{
+				Title:   "Caddy",
+				Section: "8",
+			}, dir); err != nil {
+				return caddy.ExitCodeFailedQuit, err
+			}
+			return caddy.ExitCodeSuccess, nil
+		},
+		Usage: "--directory <directory path>",
+		Short: "Generates the manual pages of Caddy commands",
+		Long: `
+Generates the manual pages of Caddy commands into the designated directory tagged into the specified section.
+
+The manual page files are generated into the directory specified by the argument of --directory. If the directory does not exist, it will be created.
+
+The manual pages are sorted into the section specified by the argument of --section.
+`,
+		Flags: func() *flag.FlagSet {
+			fs := flag.NewFlagSet("manpage", flag.ExitOnError)
+			fs.String("directory", "", "The output directory where the manpages are generated")
+			fs.String("section", "", "The section number of the generated manual pages")
+			return fs
+		}(),
+	})
 }
 
 // RegisterCommand registers the command cmd.
 // cmd.Name must be unique and conform to the
 // following format:
 //
-//    - lowercase
-//    - alphanumeric and hyphen characters only
-//    - cannot start or end with a hyphen
-//    - hyphen cannot be adjacent to another hyphen
+//   - lowercase
+//   - alphanumeric and hyphen characters only
+//   - cannot start or end with a hyphen
+//   - hyphen cannot be adjacent to another hyphen
 //
 // This function panics if the name is already registered,
 // if the name does not meet the described format, or if
@@ -378,7 +411,7 @@ func RegisterCommand(cmd Command) {
 	if !commandNameRegex.MatchString(cmd.Name) {
 		panic("invalid command name")
 	}
-	commands[cmd.Name] = cmd
+	rootCmd.AddCommand(caddyCmdToCoral(cmd))
 }
 
 var commandNameRegex = regexp.MustCompile(`^[a-z0-9]$|^([a-z0-9]+-?[a-z0-9]*)+[a-z0-9]$`)
diff --git a/cmd/main.go b/cmd/main.go
index 09246f4b4..44e339afe 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -33,6 +33,7 @@ import (
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/caddyconfig"
 	"github.com/caddyserver/certmagic"
+	"github.com/spf13/pflag"
 	"go.uber.org/zap"
 )
 
@@ -58,35 +59,9 @@ func Main() {
 		os.Args = append(os.Args, "help")
 	}
 
-	subcommandName := os.Args[1]
-	subcommand, ok := commands[subcommandName]
-	if !ok {
-		if strings.HasPrefix(os.Args[1], "-") {
-			// user probably forgot to type the subcommand
-			fmt.Println("[ERROR] first argument must be a subcommand; see 'caddy help'")
-		} else {
-			fmt.Printf("[ERROR] '%s' is not a recognized subcommand; see 'caddy help'\n", os.Args[1])
-		}
-		os.Exit(caddy.ExitCodeFailedStartup)
-	}
-
-	fs := subcommand.Flags
-	if fs == nil {
-		fs = flag.NewFlagSet(subcommand.Name, flag.ExitOnError)
-	}
-
-	err := fs.Parse(os.Args[2:])
-	if err != nil {
-		fmt.Println(err)
-		os.Exit(caddy.ExitCodeFailedStartup)
+	if err := rootCmd.Execute(); err != nil {
+		os.Exit(1)
 	}
-
-	exitCode, err := subcommand.Func(Flags{fs})
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "%s: %v\n", subcommand.Name, err)
-	}
-
-	os.Exit(exitCode)
 }
 
 // handlePingbackConn reads from conn and ensures it matches
@@ -280,7 +255,7 @@ func watchConfigFile(filename, adapterName string) {
 // Flags wraps a FlagSet so that typed values
 // from flags can be easily retrieved.
 type Flags struct {
-	*flag.FlagSet
+	*pflag.FlagSet
 }
 
 // String returns the string representation of the
@@ -326,22 +301,6 @@ func (f Flags) Duration(name string) time.Duration {
 	return val
 }
 
-// flagHelp returns the help text for fs.
-func flagHelp(fs *flag.FlagSet) string {
-	if fs == nil {
-		return ""
-	}
-
-	// temporarily redirect output
-	out := fs.Output()
-	defer fs.SetOutput(out)
-
-	buf := new(bytes.Buffer)
-	fs.SetOutput(buf)
-	fs.PrintDefaults()
-	return buf.String()
-}
-
 func loadEnvFromFile(envFile string) error {
 	file, err := os.Open(envFile)
 	if err != nil {