title: Update BOSH releases using knit
body: <p>I am using different BOSH releases, i.e., the <a href="https://github.com/cloudfoundry-community/jumpbox-boshrelease" rel="nofollow noreferrer">jumpbox-boshrelease</a> which I adapted to my requirements.
  These releases have to be maintained.
  For this, I want to download the updates from the community release and merge my own modifications into this repository.</p>
  
  <p>I just tried to use the <a href="https://github.com/pivotal-cf-experimental/knit" rel="nofollow noreferrer">knit tool</a> to perform this. However, I do not understand how it is supposed to work.
  For testing purposes I created only minor changes to the <code>README.md</code> (I added an additional line).</p>
  
  <p>My <code>starting-versions.yml</code> looks like this:</p>
  
  <pre><code>---
  starting_versions:
  - version: 0
    ref: "master"
  - version: 1
    ref: "master"
    patches:
    - "~/knit-test/test-knit.patch"
  </code></pre>
  
  <p>Does the patch file should be a git patch file?
  I tried it with a git patch file and with a file which contains all changes.
  I always receive the following error:</p>
  
  <pre><code>$ knit --repository-to-patch ~/knit-test/jumpbox-boshrelease --patch-repository ~/knit-test/jumpbox-boshrelease-mod --version 1.0.1
  Already on 'master'
  usage: git submodule [--quiet] add [-b &lt;branch&gt;] [-f|--force] [--name &lt;name&gt;] [--reference &lt;repository&gt;] [--] &lt;repository&gt; [&lt;path&gt;]
  or: git submodule [--quiet] status [--cached] [--recursive] [--] [&lt;path&gt;...]
  or: git submodule [--quiet] init [--] [&lt;path&gt;...]
  or: git submodule [--quiet] deinit [-f|--force] [--] &lt;path&gt;...
  or: git submodule [--quiet] update [--init] [--remote] [-N|--no-fetch] [-f|--force] [--rebase] [--reference &lt;repository&gt;] [--merge] [--recursive] [--] [&lt;path&gt;...]
  or: git submodule [--quiet] summary [--cached|--files] [--summary-limit &lt;n&gt;] [commit] [--] [&lt;path&gt;...]
  or: git submodule [--quiet] foreach [--recursive] &lt;command&gt;
  or: git submodule [--quiet] sync [--recursive] [--] [&lt;path&gt;...]
  </code></pre>
  
  <p>```</p>
  
  <p>I am not sure how knit is supposed to work, documentation is rare :smile:</p>