项目中需要用到 caracal-1.4.1 这个 gem，我发现它依赖 rubyzip 的版本是 1.1，但是因为跟 axlsx 依赖 rubyzip 的版本有冲突，故我的第一想法就是手动改 caracal 这个 gem 的依赖版本跟 axlsx 一样。 实操步骤，首先下载 caracal-1.4.1 这个 gem，利用 gem unpack caracal-1.4.1.gem，解压得到源码，修改 caracal.gemspec 内的依赖关系，然后在执行 gem build caracal.gemspec，报了一些警告如下：

WARNING:  no files specified
WARNING:  open-ended dependency on tilt (>= 1.4) is not recommended
  if tilt is semantically versioned, use:
    add_runtime_dependency 'tilt', '~> 1.4'
WARNING:  See http://guides.rubygems.org/specification-reference/ for help
  Successfully built RubyGem
  Name: caracal
  Version: 1.4.1
  File: caracal-1.4.1.gem

caracal.gemspec 的内容如下

# coding: utf-8
lib = File.expand_path('../lib', __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require 'caracal/version'

Gem::Specification.new do |spec|
  spec.name          = 'caracal'
  spec.version       = Caracal::VERSION
  spec.authors       = ['Trade Infomatics', 'John Dugan']
  spec.email         = ['[email protected]']
  spec.summary       = %q{ Fast, professional Microsoft Word (docx) writer for Ruby. }
  spec.description   = %q{ Caracal is a pure Ruby Microsoft Word generation library that produces professional quality MSWord documents (docx) using a simple, HTML-style DSL. }
  spec.homepage      = 'https://github.com/trade-informatics/caracal'
  spec.license       = 'MIT'

  spec.files         = `git ls-files -z`.split("\x0")
  spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
  spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
  spec.require_paths = ['lib']

  spec.add_dependency 'nokogiri', '~> 1.6'
  spec.add_dependency 'rubyzip',  '~> 1.1' //我修改的地方，改成了'~> 1.0.0'
  spec.add_dependency 'tilt',     '>= 1.4'

  spec.add_development_dependency 'bundler',  '~> 1.3'
  spec.add_development_dependency 'rake',     '~> 10.0'
  spec.add_development_dependency 'rspec',    '~> 3.0'
end

然后比较了下原始大小和重新生成的大小相差好多，一个是 4608（重新生成的 gem 大小），一个是 108544（原始 gem 大小），请教下各位这是怎么回事