linkapp: create Finder aliases

Symlinks to apps don't play well with Spotlight, but Finder alises do,
so let's create them instead.

Closes Homebrew/homebrew#14821.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Library/Contributions/cmds/brew-linkapps.rb

@@ -9,6 +9,19 @@ unless File.exist? HOME_APPS
   exit 1
 end
 
+FINDER_ALIAS_MAGIC_PREFIX = "book\x00\x00\x00\x00mark\x00\x00\x00\x00"
+
+def finder_alias?(filename)
+  return false if not File.file? filename
+  File.open(filename) do |f|
+    return f.read(FINDER_ALIAS_MAGIC_PREFIX.length) == FINDER_ALIAS_MAGIC_PREFIX
+  end
+end
+
+def create_finder_alias(from, to)
+  system %Q{osascript -e 'tell application "Finder" to make alias file to POSIX file "#{from}" at POSIX file "#{to}"' > /dev/null}
+end
+
 HOMEBREW_CELLAR.subdirs.each do |keg|
   next unless keg.subdirs
   name = keg.basename.to_s
@@ -16,16 +29,16 @@ HOMEBREW_CELLAR.subdirs.each do |keg|
   if ((f = Formula.factory(name)).installed? rescue false)
     Dir["#{f.installed_prefix}/*.app", "#{f.installed_prefix}/bin/*.app", "#{f.installed_prefix}/libexec/*.app"].each do |p|
       puts "Linking #{p}"
-      appname = File.basename(p)
+      appname = File.basename(p, ".app")
       target = HOME_APPS+"/"+appname
       if File.exist? target
-        if File.symlink? target
+        if File.symlink? target or finder_alias? target
           system "rm", target
         else
           onoe "#{target} already exists, skipping."
         end
       end
-      system "ln", "-s", p, HOME_APPS
+      create_finder_alias(p, HOME_APPS)
     end
   end
 end