compat/dependency_collector: cleanup style.

Library/Homebrew/compat/dependency_collector.rb

@@ -6,12 +6,16 @@ class DependencyCollector
   def parse_symbol_spec(spec, tags)
     case spec
     when :clt
+      odeprecated "'depends_on :clt'"
     when :autoconf, :automake, :bsdmake, :libtool
+      output_deprecation(spec, tags)
       autotools_dep(spec, tags)
     when :cairo, :fontconfig, :freetype, :libpng, :pixman
+      output_deprecation(spec, tags)
       Dependency.new(spec.to_s, tags)
     when :libltdl
       tags << :run
+      output_deprecation("libtool", tags)
       Dependency.new("libtool", tags)
     else
       _parse_symbol_spec(spec, tags)
@@ -22,4 +26,14 @@ class DependencyCollector
     tags << :build unless tags.include? :run
     Dependency.new(spec.to_s, tags)
   end
+
+  def output_deprecation(dependency, tags)
+    tags_string = if tags.length > 1
+      " => [:#{tags.join ", :"}]"
+    elsif tags.length == 1
+      " => :#{tags.first}"
+    end
+    odeprecated "'depends_on :#{dependency}'",
+                "'depends_on \"#{dependency}\"#{tags_string}'"
+  end
 end