compass config. emulates a 5th output style I'd call "optimize"

config.rb

# Require any additional compass plugins here.

if Sass::VERSION =~ /3.1/
  raise "you should upgrade to Sass version 3.2"
end

# Set this to the root of your project when deployed:
http_path = "/"
css_dir = "/css"
sass_dir = "/scss"
images_dir = "/img"
javascripts_dir = "/js"

# You can select your preferred output style here (can be overridden via the command line):
# output_style = :expanded # or 
# output_style = :nested # or 
# output_style = :compact # or
output_style = :compressed

# To enable relative paths to assets via compass helper functions. Uncomment:
relative_assets = true

# To disable debugging comments that display the original location of your selectors. Uncomment:
line_comments = false

# when using SCSS:
sass_options = {
  :syntax        => :scss,
  :unix_newlines => true
}

# auto decompress the css after save
on_stylesheet_saved do |filename|
  if File.exists?(filename)
    unminify(filename)
  end
end

def unminify(filename)
  raise "file not found #{filename}" unless File.exists? filename
  text = []
  File.open(filename, 'r:UTF-8') do |f|
    f.each_line do |line|
      line.strip!

      code = line
            .split("\t").join(" ")
            .gsub(/\s*{\s*/i, " {\n  ")
            .gsub(/;\s*/i, ";\n  ")
            .gsub(/,\s*/i, ", ")
            .gsub(/[ ]*}\s*/i, "}\n")
            .gsub(/\}/i, "\n}")
            .gsub(/\n  (?<r>[^:]+):\s*/i, "\n  " + '\k<r>: ')
            .gsub(/  @/, '@')
            .gsub(/\*\/((?<r>.*))/, "*/\n" + '\k<r>')

      text.push(code)
    end
  end
  File.open(filename, 'w:UTF-8') do |f|
    f.write(text.join("\n").strip + "\n")
  end
end

# If you prefer the indented syntax, you might want to regenerate this
# project again passing --syntax sass, or you can uncomment this:
# preferred_syntax = :sass
# and then run:
# sass-convert -R --from scss --to sass sass scss && rm -rf sass && mv scss sass