title: skip incoming file deletions when updating svn
body: <h1>Motivation</h1>
  
  <p>I'm playing around with SVN a bit lately. The problem I'm facing is as follows:</p>
  
  <ul>
  <li>Person 1 checks in some changes to section A of the project, creating revision <code>r100</code></li>
  <li>Person 2 checks out the trunk, compiles the part B of the project, and checks in some more things, creating revision <code>r101</code></li>
  <li>Person 3 checks out the trunk, compiles the part A of the project, and realizes that Person 1 forgot to check in a newly introduced file <code>a.txt</code>. Person 3 complains to Person 1 about this.</li>
  <li>Person 1 adds and commits the additional file <code>a.txt</code>, creating revision <code>r102</code>.</li>
  <li>Much later, Person 4 decides to check if some particular feature worked in part A of the project in revision <code>r101</code> and realizes that part A of the project does not compile in <code>r101</code> due to a missing file.</li>
  </ul>
  
  <p>This is what some people would consider a minor nuisance and what some people would consider a major catastrophe. But irrespective of how bad this is, I am currently writing some code that crawls a (rather large) SVN to obtain some statistics. For this, it would be useful to have the project compile successfully under as many revisions as possible, even if they are "flawed" due to missing files, such as revision <code>r102</code> in this example. For me, this is a particular problem, as there are some (almost abandoned) parts of the project that have had certain files missing for large fractions of time, while development occurred in other parts of the project. In principle, the problem could be solved (at least in my case) by using the following approach:</p>
  
  <ul>
  <li>Start with the latest revision and <code>svn up</code> to earlier revisions decrementally.</li>
  <li>When a file would otherwise be deleted by <code>svn up</code>, simply don't perform the delete.</li>
  </ul>
  
  <p>That way, the versions I'm looking at are not really the revisions of the code as they are in SVN, but have some spurious files from later revisions lying around. For the type of statistic I want to use, this is not a problem, as only files explicitly included by the master file will be counted anyhow. With that, I would be able to significantly improve my measurement.</p>
  
  <p>This, to me, brings up </p>
  
  <h1>The Question</h1>
  
  <p>How can I instruct SVN to skip incoming file deletions upon <code>svn up</code>?</p>