Add rake-fast plugin for fast rake autocompletion

plugins/rake-fast/rake-fast.plugin.zsh

+# rake-fast
+# Fast rake autocompletion plugin for oh-my-zsh
+
+# This script caches the output for later usage and significantly speeds it up.
+# It generates a .rake_tasks file in parallel to the Rakefile.
+
+# You'll want to add `.rake_tasks` to your global .git_ignore file:
+# https://help.github.com/articles/ignoring-files#global-gitignore
+
+# You can force .rake_tasks to refresh with:
+# $ rake_refresh
+
+# This is entirely based on Ullrich Schäfer's work
+# (https://github.com/robb/.dotfiles/pull/10/),
+# which is inspired by this Ruby on Rails trick from 2006:
+# http://weblog.rubyonrails.org/2006/3/9/fast-rake-task-completion-for-zsh/
+
+# Author: Kevin Bongart
+# contact@kevinbongart.net
+# http://kevinbongart.net
+# https://github.com/KevinBongart
+
+_rake_refresh () {
+  if [ -f .rake_tasks ]; then
+    rm .rake_tasks
+  fi
+  echo "Generating .rake_tasks..." > /dev/stderr
+  _rake_generate
+  cat .rake_tasks
+}
+
+_rake_does_task_list_need_generating () {
+  if [ ! -f .rake_tasks ]; then return 0;
+  else
+    accurate=$(stat -f%m .rake_tasks)
+    changed=$(stat -f%m Rakefile)
+    return $(expr $accurate '>=' $changed)
+  fi
+}
+
+_rake_generate () {
+  rake --silent --tasks | cut -d " " -f 2 > .rake_tasks
+}
+
+_rake () {
+  if [ -f Rakefile ]; then
+    if _rake_does_task_list_need_generating; then
+      echo "\nGenerating .rake_tasks..." > /dev/stderr
+      _rake_generate
+    fi
+    compadd `cat .rake_tasks`
+  fi
+}
+
+compdef _rake rake
+alias rake_refresh='_rake_refresh'