x/tools/gopls: improve output for subcommands with no flags

[ainar-g]

Currently (golang/tools@63754364767c), the output of gopls check -h looks like this:

show diagnostic results for the specified file

Usage: check [flags] <filename>

Example: show the diagnostic results of this file:

  $ gopls check internal/lsp/cmd/check.go

	gopls check flags are:

That is, no flags are documented. If gopls check actually has flags, they should probably be documented, and if not, the output should probably not mention them at all.

[rentziass]

I believe this was fixed by golang.org/cl/284215?

[ainar-g]

@rentziass, I've checked gopls from master, and the message is better, but there is still the [flags] in there:

$ gopls check -h
  show diagnostic results for the specified file

  Usage: check [flags] <filename>

  Example: show the diagnostic results of this file:

    $ gopls check internal/lsp/cmd/check.go

Ironically, the -h flag, which I used to get this message, isn't documented in the message itself.

[rentziass]

I see, that probably doesn't come from the commands themselves but something higher up. Let me have a look.

[gopherbot]

Change https://golang.org/cl/357994 mentions this issue: internal/tool: remove [flags] when not necessary

[ianthehat]

gopls check does support flags, it is the default flag set that applies to all commands. This is not well documented though, and the help is confusing. The same thing is true of many of the other sub-commands.