Import RubyGems trunk revision 1493.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@13862 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/commands/help_command.rb

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+require 'rubygems/command'
+
+class Gem::Commands::HelpCommand < Gem::Command
+
+  # :stopdoc:
+  EXAMPLES = <<-EOF
+Some examples of 'gem' usage.
+
+* Install 'rake', either from local directory or remote server:
+
+    gem install rake
+
+* Install 'rake', only from remote server:
+
+    gem install rake --remote
+
+* Install 'rake' from remote server, and run unit tests,
+  and generate RDocs:
+
+    gem install --remote rake --test --rdoc --ri
+
+* Install 'rake', but only version 0.3.1, even if dependencies
+  are not met, and into a specific directory:
+
+    gem install rake --version 0.3.1 --force --install-dir $HOME/.gems
+
+* List local gems whose name begins with 'D':
+
+    gem list D
+
+* List local and remote gems whose name contains 'log':
+
+    gem search log --both
+
+* List only remote gems whose name contains 'log':
+
+    gem search log --remote
+
+* Uninstall 'rake':
+
+    gem uninstall rake
+
+* Create a gem:
+
+    See http://rubygems.rubyforge.org/wiki/wiki.pl?CreateAGemInTenMinutes
+
+* See information about RubyGems:
+
+    gem environment
+
+* Update all gems on your system:
+
+    gem update
+  EOF
+
+  PLATFORMS = <<-'EOF'
+RubyGems platforms are composed of three parts, a CPU, an OS, and a
+version.  These values are taken from values in rbconfig.rb.  You can view
+your current platform by running `gem environment`.
+
+RubyGems matches platforms as follows:
+
+  * The CPU must match exactly, unless one of the platforms has
+    "universal" as the CPU.
+  * The OS must match exactly.
+  * The versions must match exactly unless one of the versions is nil.
+
+For commands that install, uninstall and list gems, you can override what
+RubyGems thinks your platform is with the --platform option.  The platform
+you pass must match "#{cpu}-#{os}" or "#{cpu}-#{os}-#{version}".  On mswin
+platforms, the version is the compiler version, not the OS version.  (Ruby
+compiled with VC6 uses "60" as the compiler version, VC8 uses "80".)
+
+Example platforms:
+
+  x86-freebsd        # Any FreeBSD version on an x86 CPU
+  universal-darwin-8 # Darwin 8 only gems that run on any CPU
+  x86-mswin32-80     # Windows gems compiled with VC8
+
+When building platform gems, set the platform in the gem specification to
+Gem::Platform::CURRENT.  This will correctly mark the gem with your ruby's
+platform.
+  EOF
+  # :startdoc:
+
+  def initialize
+    super 'help', "Provide help on the 'gem' command"
+  end
+
+  def arguments # :nodoc:
+    args = <<-EOF
+      commands      List all 'gem' commands
+      examples      Show examples of 'gem' usage
+      <command>     Show specific help for <command>
+    EOF
+    return args.gsub(/^\s+/, '')
+  end
+
+  def usage # :nodoc:
+    "#{program_name} ARGUMENT"
+  end
+
+  def execute
+    command_manager = Gem::CommandManager.instance
+    arg = options[:args][0]
+
+    if begins? "commands", arg then
+      out = []
+      out << "GEM commands are:"
+      out << nil
+
+      margin_width = 4
+
+      desc_width = command_manager.command_names.map { |n| n.size }.max + 4
+
+      summary_width = 80 - margin_width - desc_width
+      wrap_indent = ' ' * (margin_width + desc_width)
+      format = "#{' ' * margin_width}%-#{desc_width}s%s"
+
+      command_manager.command_names.each do |cmd_name|
+        summary = command_manager[cmd_name].summary
+        summary = wrap(summary, summary_width).split "\n"
+        out << sprintf(format, cmd_name, summary.shift)
+        until summary.empty? do
+          out << "#{wrap_indent}#{summary.shift}"
+        end
+      end
+
+      out << nil
+      out << "For help on a particular command, use 'gem help COMMAND'."
+      out << nil
+      out << "Commands may be abbreviated, so long as they are unambiguous."
+      out << "e.g. 'gem i rake' is short for 'gem install rake'."
+
+      say out.join("\n")
+
+    elsif begins? "options", arg then
+      say Gem::Command::HELP
+
+    elsif begins? "examples", arg then
+      say EXAMPLES
+
+    elsif begins? "platforms", arg then
+      say PLATFORMS
+
+    elsif options[:help] then
+      command = command_manager[options[:help]]
+      if command
+        # help with provided command
+        command.invoke("--help")
+      else
+        alert_error "Unknown command #{options[:help]}.  Try 'gem help commands'"
+      end
+
+    elsif arg then
+      possibilities = command_manager.find_command_possibilities(arg.downcase)
+      if possibilities.size == 1
+        command = command_manager[possibilities.first]
+        command.invoke("--help")
+      elsif possibilities.size > 1
+        alert_warning "Ambiguous command #{arg} (#{possibilities.join(', ')})"
+      else
+        alert_warning "Unknown command #{arg}. Try gem help commands"
+      end
+
+    else
+      say Gem::Command::HELP
+    end
+  end
+
+end
+