title: Source tree .gitignore to ignore everything but specific directories/files
body: <p>I've seen many <a href="https://stackoverflow.com/questions/5241644/using-gitignore-to-ignore-everything-but-specific-directories">examples</a> and they pretty much say the same but for some reason I cannot get it to work using SourceTree.
  My folder structure shown below, i want to ignore everything except for folder3 and all it's content, folder2_3_2_1, all it's content and the .ignore file.</p>
  
  <pre><code>folder1
  folder2
     folder2_1
     folder2_2
     folder2_3
       folder2_3_1
       folder2_3_2
            folder2_3_2_1
               someOtherFile1.php
               someOtherFile12php
               someNewFolder
       folder2_3_3
     folder2_4
  folder3
  .ignore
  somefile.php
  somefile2.php
  </code></pre>
  
  <p>in my .ignore I have the following</p>
  
  <pre><code># Ignore everything
  /*
  
  #except for
  !.gitignore
  !folder3/
  !folder2/folder2_3/folder2_3_2/
  </code></pre>
  
  <p>Strange thing is, if I don't ignore anything and I'm able to see all my files in my unstaged files panel, if I right click and ignore someOtherFile.php and select the option to ignore everything beneath, it does the opposite, sourceTree ignores it's folder (i.e. folder2_3_2_1) and everything within!</p>
  
  <p>SourceTree V 2.3.1.0</p>
  
  <p>Thank you in advance</p>