title: After moving git submodule to another directory it fails with error 'git status --porcelain' failed in submodule
body: <p>Initially I had the following (simplified) repo structure:</p>
  
  <pre><code>MyRepo
     external1/MySub (git submodule)
     .gitsubmodules
  </code></pre>
  
  <p>Where</p>
  
  <pre><code>$ cat .gitsubmodules
  
    [submodule "external1/MySub"]
    path = external1/MySub
    url = user@repo:/remoterepo/externals/MySub.git
  </code></pre>
  
  <p>I then wanted to move MySubmodule to another directory in the same git repository, e.g., <em>external2</em> so the structure is as follows:</p>
  
  <pre><code>MyRepo
     external2/MySub (git submodule)
     .gitsubmodules
  </code></pre>
  
  <hr>
  
  <p>What I did, and thought is enough, I simply moved (via OS <code>mv</code>) the <em>external1/MySub</em> directory to <em>external2/MySub</em> and edited the <em>.gitsubmodules</em> file to:</p>
  
  <pre><code>$ cat .gitsubmodules
  
    [submodule "external2/MySub"]
    path = external2/MySub
    url = user@repo:/remoterepo/externals/MySub.git
  </code></pre>
  
  <p>After this change, I get the following error:</p>
  
  <pre><code>$ git status
  
    fatal: Could not chdir to '../../../../../repo/external/MySub': No such file or directory
    fatal: 'git status --porcelain' failed in submodule repo/external2/MySub
  </code></pre>
  
  <hr>
  
  <p>What am I missing? Any other changes need to be done for such move to work?</p>
  
  <p>(I'm using git version 1.8.3rc3 on Windows 8.1)</p>