Some bulletproofing for bash completion script.

Since Homebrew's Library doesn't have to be linked under prefix,
we need to do some extra work in the bash completion script to
support this configuration.

Added a "--repository" option to brew, and updated the completion
script to use paths relative to this location.

Library/Contributions/brew_bash_completion.sh

@@ -21,8 +21,7 @@ _brew_to_completion()
         return 0
     # Subcommands
     else
-        brew_base=`which brew`
-        brew_base=`dirname ${brew_base}`/..
+        brew_base=`brew --repository`
         
         case ${prev} in
             # Commands that take a formula...

bin/brew

@@ -75,6 +75,8 @@ begin
   case arg = ARGV.shift
   when '--prefix'
     puts HOMEBREW_PREFIX
+  when '--repository'
+    puts HOMEBREW_REPOSITORY
   when '--config'
     dump_config