title: Avoiding "warning: There are too many unreachable loose objects" during git svn clone/fetch
body: <p>When running a <code>git svn clone</code> or <code>git svn fetch</code> against a large Subversion repository (100k+ commits), the fetch regularly stops with:</p>
  
  <pre><code>Auto packing the repository in background for optimum performance.
  See "git help gc" for manual housekeeping.
  error: The last gc run reported the following. Please correct the root cause and remove .git/gc.log.
  Automatic cleanup will not be performed until the file is removed.
  
  warning: There are too many unreachable loose objects; run 'git prune' to remove them.
  
  gc --auto: command returned error: 255
  </code></pre>
  
  <p>In order to recover I have to follow the instructions, run a more aggressive prune and gc, remove the log-file and continue, only to have it happen again after another batch of say 10k commits are read.</p>
  
  <p>How can this problem be avoided?</p>