heroku/heroku — pull request #1005 by guilleiguaran (2014-01-18 17:00:50+00:00)
Title: Show usage in plugins:install/uninstall commands when an argument is not provided

Right now a TypeError (no implicit conversion of nil into String) is raised

```
% heroku plugins:install
! Heroku client internal error.
! Search for help at: https://help.heroku.com
! Or report a bug at: https://github.com/heroku/heroku/issues/new

Error: no implicit conversion of nil into String (TypeError)
Backtrace: /Users/guille/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/heroku-3.2.2/lib/heroku/plugin.rb:159:in `basename'
/Users/guille/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/heroku-3.2.2/lib/heroku/plugin.rb:159:in `guess_name'
/Users/guille/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/heroku-3.2.2/lib/heroku/plugin.rb:98:in `initialize'
/Users/guille/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/heroku-3.2.2/lib/heroku/command/plugins.rb:41:in `new'
/Users/guille/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/heroku-3.2.2/lib/heroku/command/plugins.rb:41:in `install'
/Users/guille/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/heroku-3.2.2/lib/heroku/command.rb:218:in `run'
/Users/guille/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/heroku-3.2.2/lib/heroku/cli.rb:28:in `start'
/Users/guille/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/heroku-3.2.2/bin/heroku:17:in `'
/Users/guille/.rbenv/versions/2.1.0/bin/heroku:23:in `load'
/Users/guille/.rbenv/versions/2.1.0/bin/heroku:23:in `

'

Command: heroku plugins:install
Plugins: heroku-config-versions
Version: heroku-gem/3.2.2 (x86_64-darwin13.0) ruby/2.1.0
```

Usually I run the commands without arguments when I want to know the correct usage.