title: No submodule mapping found in .gitmodules for path 'craft/config'
body: <p>I've changed some database settings in a project and can't commit the DB file. It doesn't even show up as modified. This codebase is copied from another Craft site I built, which a new repository was created for. It is running Craft CMS 2.6.2903.</p>
  
  <pre><code>$ git add craft/config/db.php
  fatal: Pathspec 'craft/config/db.php' is in submodule 'craft/config'
  
  fatal: no submodule mapping found in .gitmodules for path 'craft/config'
  </code></pre>
  
  <p>There's no .gitmodules file in the repo (or in any of my other Craft sites) and it doesn't make sense for the DB file or the other config files to be in a submodule.</p>
  
  <p>I'm really confused now as I can't even find a relevant reference to that submodule in the .git folder.</p>
  
  <pre><code>grep -ro "craft/config" .
  Binary file ./index matches
  </code></pre>
  
  <p>Given I can't find it I'm not sure what to do next.</p>