my_remover.rb

# Reads unified diff file of CRuby documents between "before" and "after"
# from standard input and removes fixed line number changes

class MyRemover
  def initialize
    @lines = STDIN.readlines
    @pos = 0
    puts read_file_sections.flatten.join
  end

  def read_file_sections
    results = []
    file_section = []
    until @lines.size <= @pos
      if @lines[@pos] =~ /^diff -ru/
        file_section << @lines[@pos]
        file_section << @lines[@pos + 1]
        file_section << @lines[@pos + 2]
        @pos += 3
        diff_sections = read_diff_sections
        unless diff_sections.empty? or file_section.first =~ /\.js/
          results << file_section
          results << diff_sections
        end
        file_section = []
      else
        puts "WTF!?!?!?!??!"
        puts @lines[@pos]
        @pos += 1
      end
    end
    results
  end

  def read_diff_sections
    results = []
    until @lines.size <= @pos
      case @lines[@pos]
      when /^@@.+@@$/
        head = @lines[@pos]
        @pos += 1
        diff_result = read_diff_section(head)
        results.push(diff_result) if diff_result
      when /^diff -ru/
        break
      else
        puts "WTF?"
        puts @lines[@pos]
        @pos += 1
      end
    end
    results
  end

  def read_diff_section(head)
    diff_section = []
    until @lines.size <= @pos
      if (@lines[@pos] =~ /^@@.+@@$/ or @lines[@pos] =~ /^diff -ru/)
        break
      end
      diff_section << @lines[@pos]
      @pos += 1
    end
    if diff_section.select { |l| l =~ /^[-+]/ }.all? { |l| l =~ %r{^[-+] *<pre><span class="ruby-comment"># File .+, line \d+</span>} }
      nil
    else
      [head].concat(diff_section)
    end
  end
end

my_remover = MyRemover.new
my_remover.read_file_sections