adding zsh completion

Library/Contributions/brew_zsh_completion.zsh

@@ -0,0 +1,65 @@
+#compdef brew
+
+# Brew ZSH completion function
+# Drop this somewhere in your $fpath (like /usr/share/zsh/site-functions)
+# and rename it _brew
+#
+# altered from _fink
+
+_brew_all_formulae() {
+  formulae=(`brew search`)
+}
+
+_brew_installed_formulae() {
+  installed_formulae=(`brew list`)
+}
+
+local -a _1st_arguments
+_1st_arguments=(
+  'install:install a formula'
+  'remove:remove a formula'
+  'search:search for a formula (/regex/ or string)'
+  'list:list files in a formula or not-installed formulae'
+  'link:link a formula'
+  'unlink:unlink a formula'
+  'home:visit the homepage of a formula or the brew project'
+  'info:information about a formula'
+  'prune:remove dead links'
+  'update:freshen up links'
+  'log:git commit log for a formula'
+  'create:create a new formula'
+  'edit:edit a formula'
+)
+
+local expl
+local -a formula installed_formulae
+
+_arguments \
+  '(-v --verbose)'{-v,--verbose}'[verbose]' \
+  '(--version)--version[version information]' \
+  '(--prefix)--prefix[where brew lives on this system]' \
+  '(--cache)--cache[brew cache]' \
+  '*:: :->subcmds' && return 0
+
+if (( CURRENT == 1 )); then
+  _describe -t commands "brew subcommand" _1st_arguments
+  return
+fi
+
+case "$words[1]" in
+  list)
+    _arguments \
+      '(--unbrewed)--unbrewed[files in brew --prefix not controlled by brew]' \
+      '1: :->forms' &&  return 0
+      
+      if [[ "$state" == forms ]]; then
+        _brew_installed_formulae
+        _requested installed_formulae expl 'installed formulae' compadd -a installed_formulae
+      fi ;;
+  install|home|log|info)
+    _brew_all_formulae
+    _wanted formulae expl 'all formulae' compadd -a formulae ;;
+  remove|edit|xo)
+    _brew_installed_formulae
+    _wanted installed_formulae expl 'installed formulae' compadd -a installed_formulae ;;
+esac