From: Joel VanderWerf <joelvanderwerf@...>
Date: 2010-04-20T08:55:38+09:00
Subject: Re: Documenting Rakefile using rdoc

Here's another version:

task "tasks" do
   Rake::Task.tasks.each do | tsk |
     next if tsk.name =~ /:/ or not tsk.full_comment
     printf "rake %-19s# %s\n", tsk.name, tsk.full_comment
   end
end

namespace "tasks" do
   rule /.*/ do |t|
     pats = t.name.split(":")[1..-1].map {|pat| Regexp.new("\\A#{pat}\\z")}
     Rake::Task.tasks.each do | tsk |
       next unless tsk.full_comment
       parts = tsk.name.split(":")
       next unless parts.size <= pats.size + 1
       next unless pats.zip(parts).all? {|pat, part| pat === part}
       printf "rake %-19s# %s\n", tsk.name, tsk.full_comment
     end
   end
end

Use it like this:

$ rake tasks  # show all top level tasks
$ rake tasks:internals  # show all tasks in "internals" namespace
$ rake tasks:internals:'build.*' # show all tasks in "internals" 
namespace whose name begins with build

It probably still needs some tinkering...