chore(cli): clean up generated usage strings for config commands (fixes #10462) (#10463)

* Show proper subcommand prefix in generated config CLI.
* Remove useless author info and copy command group description.
* Really accept (implicit) -h and --help flags.

These were disabled by HideHelp, leading to an error message in every
usage output.  This way, the flags get documented as well.

* Override AppHelpTemplate to better match Kong's style.
* Override (Sub)commandHelpTemplate to better match Kong's style.
* Use <command> and [flags] like Kong.

Signed-off-by: André Colomb <src@andre.colomb.de>

cmd/syncthing/cli/config.go

@@ -19,6 +19,53 @@ import (
 	"github.com/urfave/cli"
 )
 
+// Try to mimic the kong output format through custom help templates
+var customAppHelpTemplate = `Usage: {{if .UsageText}}{{.UsageText}}{{else}}{{.HelpName}}{{if .Commands}} <command> [flags]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}
+
+{{.Description}}{{if .VisibleFlags}}
+
+Flags:
+  {{range $index, $option := .VisibleFlags}}{{if $index}}
+  {{end}}{{$option}}{{end}}{{end}}{{if .VisibleCommands}}
+
+Commands:{{range .VisibleCategories}}{{if .Name}}
+
+  {{.Name}}:{{range .VisibleCommands}}
+    {{join .Names ", "}}{{"\t"}}{{.Usage}}{{end}}{{else}}{{range .VisibleCommands}}
+  {{join .Names ", "}}{{"\t"}}{{.Usage}}{{end}}{{end}}{{end}}{{end}}
+`
+
+var customCommandHelpTemplate = `Usage: {{if .UsageText}}{{.UsageText}}{{else}}{{.HelpName}}{{if .VisibleFlags}} [flags]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}
+
+{{.Usage}}{{if .VisibleFlags}}
+
+Flags:
+  {{range $index, $option := .VisibleFlags}}{{if $index}}
+  {{end}}{{$option}}{{end}}{{end}}{{if .Category}}
+
+Category:
+  {{.Category}}{{end}}{{if .Description}}
+
+{{.Description}}{{end}}
+`
+
+var customSubcommandHelpTemplate = `Usage: {{if .UsageText}}{{.UsageText}}{{else}}{{.HelpName}} <command>{{if .VisibleFlags}} [flags]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}{{if .Description}}
+
+{{.Description}}{{else}}{{if .Usage}}
+
+{{.Usage}}{{end}}{{end}}{{if .VisibleFlags}}
+
+Flags:
+  {{range $index, $option := .VisibleFlags}}{{if $index}}
+  {{end}}{{$option}}{{end}}{{end}}{{if .VisibleCommands}}
+
+Commands:{{range .VisibleCategories}}{{if .Name}}
+
+  {{.Name}}:{{range .VisibleCommands}}
+    {{join .Names ", "}}{{"\t"}}{{.Usage}}{{end}}{{else}}{{range .VisibleCommands}}
+  {{join .Names ", "}}{{"\t"}}{{.Usage}}{{end}}{{end}}{{end}}{{end}}
+`
+
 type configHandler struct {
 	original, cfg config.Configuration
 	client        APIClient
@@ -29,13 +76,18 @@ type configCommand struct {
 	Args []string `arg:"" default:"-h"`
 }
 
-func (c *configCommand) Run(ctx Context, _ *kong.Context) error {
+func (c *configCommand) Run(ctx Context, outerCtx *kong.Context) error {
 	app := cli.NewApp()
-	app.Name = "syncthing"
+	app.Name = "syncthing cli config"
-	app.Author = "The Syncthing Authors"
+	app.HelpName = "syncthing cli config"
+	app.Description = outerCtx.Selected().Help
 	app.Metadata = map[string]interface{}{
 		"clientFactory": ctx.clientFactory,
 	}
+	app.CustomAppHelpTemplate = customAppHelpTemplate
+	// Override global templates, as this is out only usage of the package
+	cli.CommandHelpTemplate = customCommandHelpTemplate
+	cli.SubcommandHelpTemplate = customSubcommandHelpTemplate
 
 	h := new(configHandler)
 	h.client, h.err = ctx.clientFactory.getClient()
@@ -56,6 +108,8 @@ func (c *configCommand) Run(ctx Context, _ *kong.Context) error {
 
 	app.Commands = commands
 	app.HideHelp = true
+	// Explicitly re-add help only as flags, not as commands
+	app.Flags = []cli.Flag{cli.HelpFlag}
 	app.Before = h.configBefore
 	app.After = h.configAfter