Support 'cabal help' in addition to 'cabal --help'

[bos]

(Imported from Trac #272, reported by @tibbe on 2008-04-29)

Many tools with a Cabal like interface (e.g. darcs, git, subversion, perforce) support

<program name> help [<command>]

where leaving out the command gives the same behavior as

<program name> --help

Supporting the same interface as may other tools would be nice for new users (who are likely to type help!) and experienced users as well (same syntax for all your tools). The first, and probably easiest thing would be to just support 'cabal help' but I would be nice with 'cabal help <command>' as well.

[bos]

(Imported comment by @dcoutts on 2008-04-29)

Done!

Wed Apr 30 14:37:40 BST 2008  Duncan Coutts <duncan@haskell.org>
  * Add help command as per ticket #272
  "cabal help" behaves like "cabal --help"
  "cabal help cmd" behaves like "cabal cmd --help"
  Should still work with command line completion.