title: Edit Auto merge commit message
body: <p>I want to edit the default merge message of Git, I've a server side hook declared, that validates if the commit message begins with 7 numbers 
  (Eg. "1234567 - solve the bug 3").</p>
  
  <p>Sometimes we do a local merge between 2 branches, so, the merge generates a default commit message  without the numbers like this: "Merge branch 'newBranch' into newBranch2"</p>
  
  <p>If the developer doesn't see the auto merge message, and do another commit(s) after the merge, when he'll push the branch to the assembla the server decline the push cause the merge message is wrong.</p>
  
  <p>How can I change the prefix of the auto commit message to "0000000 - "
  without "--amend" and without "git merge -m "?</p>