feat: switch to a simplified version of flag

Eventually, I want to write a flag-parsing library of my own.  But for
now, I can use flag from the standard library.  However, to simplify my
code, I have removed a lot from flag.

Most importantly, this version of flag no longer special cases "-h" or
"--help" and it does not display usage.

cmd/gitmirror/main.go

@@ -8,5 +8,5 @@ import (
 )
 
 func main() {
-	os.Exit(cli.Gitmirror(os.Args))
+	os.Exit(cli.Gitmirror(os.Args[1:]))
 }

go.mod

@@ -2,4 +2,7 @@ module github.com/telemachus/gitmirror
 
 go 1.23.4
 
-require github.com/google/go-cmp v0.6.0
+require (
+	github.com/MakeNowJust/heredoc v1.0.0
+	github.com/google/go-cmp v0.6.0
+)

go.sum

@@ -1,2 +1,4 @@
+github.com/MakeNowJust/heredoc v1.0.0 h1:cXCdzVdstXyiTqTvfqk9SDHpKNjxuom+DOlyEeQ4pzQ=
+github.com/MakeNowJust/heredoc v1.0.0/go.mod h1:mG5amYoWBHf8vpLOuehzbGGw0EHxpZZ6lCpQ4fNJ8LE=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=

internal/cli/app.go

@@ -8,7 +8,7 @@ import (
 	"path/filepath"
 	"strings"
 
-	"github.com/telemachus/gitmirror/internal/optionparser"
+	"github.com/telemachus/gitmirror/internal/flag"
 )
 
 type appEnv struct {
@@ -18,29 +18,41 @@ type appEnv struct {
 	home    string
 	storage string
 	exitVal int
+	help    bool
 	quiet   bool
+	version bool
 }
 
 func appFrom(args []string) (*appEnv, error) {
 	app := &appEnv{cmd: cmd, exitVal: exitSuccess}
 
-	op := optionparser.NewOptionParser()
-	op.On("-c", "--config FILE", "Use FILE as config file (default ~/.gitmirror.json)", &app.config)
-	op.On("-q", "--quiet", "Print only error messages", &app.quiet)
-	op.On("--version", "Print version and exit", version)
-	op.Command("clone", "Clone git repositories using `git clone --mirror`")
-	op.Command("update|up", "Update git repositories using `git remote update`")
-	op.Command("sync", "Run both update and clone (in that order)")
-	op.Start = 24
-	op.Banner = "Usage: gitmirror [options] <subcommand>"
-	op.Coda = "\nFor more information or to file a bug report visit https://github.com/telemachus/gitmirror"
+	fs := flag.NewFlagSet("gitmirror")
+	fs.StringVar(&app.config, "config", "", "")
+	fs.StringVar(&app.config, "c", "", "")
+	fs.BoolVar(&app.help, "help", false, "")
+	fs.BoolVar(&app.help, "h", false, "")
+	fs.BoolVar(&app.quiet, "quiet", false, "")
+	fs.BoolVar(&app.quiet, "q", false, "")
+	fs.BoolVar(&app.version, "version", false, "")
 
-	// Do not continue if we cannot parse and validate arguments or get the
-	// user's home directory.
-	if err := op.ParseFrom(args); err != nil {
+	if err := fs.Parse(args); err != nil {
 		return nil, err
 	}
-	if err := validate(op.Extra); err != nil {
+
+	// Quick and dirty, but why be fancy in these cases?
+	if app.help {
+		fmt.Print(_usage)
+		os.Exit(exitSuccess)
+	}
+	if app.version {
+		fmt.Printf("%s %s\n", cmd, cmdVersion)
+		os.Exit(exitSuccess)
+	}
+
+	// Do not continue if we cannot parse and validate arguments or get the
+	// user's home directory.
+	extraArgs := fs.Args()
+	if err := validate(extraArgs); err != nil {
 		return nil, err
 	}
 	home, err := os.UserHomeDir()
@@ -52,7 +64,7 @@ func appFrom(args []string) (*appEnv, error) {
 		app.config = filepath.Join(home, config)
 	}
 	app.storage = filepath.Join(home, storage)
-	app.subCmd = op.Extra[0]
+	app.subCmd = extraArgs[0]
 
 	return app, nil
 }
@@ -83,9 +95,3 @@ func validate(extra []string) error {
 
 	return nil
 }
-
-// Quick and dirty, but why be fancy in this case?
-func version() {
-	fmt.Printf("%s %s\n", cmd, cmdVersion)
-	os.Exit(exitSuccess)
-}

internal/cli/usage.go

@@ -0,0 +1,21 @@
+package cli
+
+import "github.com/MakeNowJust/heredoc"
+
+var _usage = heredoc.Docf(`
+	usage: gitmirror [options] <subcommand> [options]
+
+	Options
+	    -c, --config=FILE	Use FILE as config file (default ~/.gitmirror.json)
+	    -q, --quiet		Print only error messages
+
+	    -h, --help		Print this help and exit
+	        --version	Print version and exit
+
+	Subcommands
+	    clone		Clone git repositories using %[1]sgit clone --mirror%[1]s
+	    update|up		Update git repositories using %[1]sgit remote update%[1]s
+	    sync		Run both update and clone (in that order)
+
+	For more information or to file a bug report visit https://github.com/telemachus/gitmirror
+	`, "`")