gistfile1.rb

#!/usr/bin/env ruby

LOCKFILE_NAME  = "Gemfile.lock"

lockfile = File.readlines(LOCKFILE_NAME)

# Finds where the gem dependency tree begins
def beginning(gem_name, lockfile)
  lockfile.each_with_index do |line, index|
    if line.include?("specs:") && lockfile[index+1].include?(gem_name)
      # traverse back until GIT
      until (prev_line ||= "").include?("GIT")
        prev_line = lockfile[index = index.pred]
      end

      return index
    end
  end

  false
end

# Finds where the gem dependency tree ends
def ending(beginning, lockfile)
  lockfile.drop(beginning).each_with_index do |line, index|
    return index if line == "\n"
  end

  false
end

if b = beginning(ARGV[0], lockfile)
  e = ending(b, lockfile) + b

  lockfile.slice!(b..e)

  # Writes the lockfile without the gem dependency tree
  File.write(LOCKFILE_NAME, lockfile.join)
end

# Ready to bundle
IO.popen('bundle') { |f| puts f.read }