title: How to resolve git submodule conflict if submodule is not initialized
body: <p>I have two branches <code>A</code> and <code>B</code>. Both contain a submodule (in the folder <code>sub</code>), however at different commits (which do not fast-forward from one to another).</p>
  
  <pre><code>A  B
  | /
  BASE
  </code></pre>
  
  <p>I've checked out <code>A</code>, but the submodule isn't initialized yet. Now I merge <code>B</code> and I get a conflict on the submodule.</p>
  
  <pre><code>$ git status
  Unmerged paths:
    (use "git add &lt;file&gt;..." to mark resolution)
  
          both modified:   sub
  </code></pre>
  
  <p>Issuing <code>git checkout --ours sub</code> does nothing (if the submodule is initialized it works, also <code>git checkout-index -f --stage=2 -- sub</code> does not work). <code>git add sub</code> causes the error <code>error: pathspec 'sub' did not match any file(s) known to git.</code>.</p>
  
  <pre><code>$ git diff sub
  diff --cc sub
  index 533da4e,ab2af77..0000000
  --- a/sub
  +++ b/sub
  @@@ -1,1 -1,1 +1,1 @@@
  - Subproject commit 533da4ea00703f4ad6d5518e1ce81d20261c40c0
   -Subproject commit ab2af775ec467ebb328a7374653f247920f258f3
  ++Subproject commit 0000000000000000000000000000000000000000
  </code></pre>
  
  <p><code>git submodule init -- sub</code> does nothing. Also <code>git submodule update --init --force -- sub</code> does not work: <code>Skipping unmerged submodule sub</code>.</p>
  
  <p>So, how can I resolve this submodule conflict (without aborting the merge and retry after initializing the submodule)?</p>