cmd/cue: forbid cue help help in favor of cue help

Requesting the help text for the help command itself is a bit silly.
`cue help` already describes how to query help for commands or topics.
Fail even though "help" is a valid command, just a special one.

This means that the help command no longer needs a long help text.
While here, slightly expand its short help text to clarify
that it also covers additional help topics beyond commands.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: I9f8541133981a7c7c3838f1783e9c89dbbe0bbcb
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1195931
Reviewed-by: Jonathan Matthews <github@hello.jonathanmatthews.com>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Paul Jolly <paul@myitcv.io>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>

cmd/cue/cmd/help.go

@@ -37,16 +37,18 @@ import (
 func newHelpCmd(c *Command) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "help [command]",
-		Short: "Help about any command",
-		Long: `Help provides help for any command in the application.
-Simply type ` + c.Name() + ` help [path to command] for full details.`,
+		Short: "show help text for a command or topic",
 		Run: func(_ *cobra.Command, args []string) {
 			findCmd := func() (*cobra.Command, bool) {
 				cmd, rest, err := c.Root().Find(args)
 				found := cmd != nil && err == nil && len(rest) == 0
 				return cmd, found
 			}
 			cmd, found := findCmd()
+			// Treat `cue help help` as an unknown help topic; just use `cue help`.
+			if found && cmd.Name() == "help" {
+				cmd, found = nil, false
+			}
 			isCmd := len(args) > 0 && args[0] == "cmd"
 			if isCmd {
 				// args is one of:

cmd/cue/cmd/root.go

@@ -177,6 +177,14 @@ func New(args []string) (*Command, error) {
 	cmd := &cobra.Command{
 		Use:   "cue",
 		Short: "cue emits configuration files to user-defined commands.",
+		// TODO(mvdan): the text below should not jump straight into `cue cmd`,
+		// and instead give a high level overview of CUE and its commands.
+		// TODO(mvdan): cobra's help text template ends with
+		//     Use "cue [command] --help" for more information about a command.
+		// which isn't great; use our own template to say
+		//     Use "cue help [command]" for more information about a command.
+		// TODO(mvdan): cobra's help text template suggests help topics
+		// such as `cue inputs`; swap with `cue help inputs`.
 		Long: `cue evaluates CUE files, an extension of JSON, and sends them
 to user-defined commands for processing.
 
@@ -256,6 +264,8 @@ For more information on writing CUE configuration files see cuelang.org.`,
 	cmd.Flag("help").Hidden = true
 
 	// "help" is treated as a special command by cobra.
+	// TODO(mvdan): hide this command; `cue help` showing itself in the list of commands
+	// is not particularly helpful, and we already mention it as the way to get help.
 	cmd.SetHelpCommand(newHelpCmd(c))
 
 	// For `cue mycmd` to be a shortcut for `cue cmd mycmd`.

cmd/cue/cmd/testdata/script/help.txtar

@@ -48,6 +48,12 @@ stderr -count=1 '^Available Commands:$'
 stderr -count=1 'Unknown help topic: mod missing'
 stderr -count=1 '^Available Commands:$'
 
+# Requesting the help text for the help command itself is a bit silly.
+# `cue help` already describes how to query help for commands or topics.
+# Fail even though technically "help" is a valid command, just a special one.
+! exec cue help help
+stderr -count=1 'Unknown help topic: help'
+
 -- stdout.golden --
 cue evaluates CUE files, an extension of JSON, and sends them
 to user-defined commands for processing.
@@ -81,7 +87,7 @@ Available Commands:
   fix            rewrite packages to latest standards
   fmt            formats CUE configuration files
   get            add dependencies to the current module
-  help           Help about any command
+  help           show help text for a command or topic
   import         convert other formats to CUE files
   login          log into a CUE registry
   mod            module maintenance