title: Gulp doesn't copy all files as expected
body: <p>I tried to create a gulpfile.js for my personal website project. I've never done this before but with a little 'trial and error' it now works in an acceptable way.</p>
  
  <p>The only thing that doesn't work even after 1000 modifications is simple copying files and folders.</p>
  
  <pre><code>var files = {
    data_src : [
      './files.json',
      'data/**/*.*'
    ],
    distribution_dest : '_distribution'
  };
  
  gulp.task('copy-data', function() {
    gulp.src(files.data_src, { base: './' })
      .pipe(gulp.dest(files.distribution_dest))
      .pipe(notify({message: 'Data copied for distribution!'}));
  });
  </code></pre>
  
  <p>This should copy all sub-folders and files to the <code>gulp.dest</code>. But it copies only half of them, some folders will be ignored even if I change their names etc. (no special characters, same subfolder structure as the once that got copied correctly ...) - nothing worked. I just can't see any pattern in this.</p>
  
  <p>There is no error message while running gulp. Nothing that would help me find the error.</p>
  
  <p>Why are some folders or files excluded from copying?</p>
  
  <hr>
  
  <p>I use <code>base</code> to keep the folder / sub-folder structure; tried with and without 'base' -> no effects on the copying process.</p>
  
  <p>I also changed the position of the 'copy-data' task in the run-list. Actually it's the first task to run. There seems to be no change in behavior no matter if it's the first or the last one.</p>
  
  <pre><code>gulp.task('default', function() {
    gulp.run('copy-data', 'custom-sass', 'framework-sass', 'custom-js', 'framework-js', 'replace-tags', 'browser-sync');
      ... some watches ...
  });
  </code></pre>
  
  <p>The structure of the data folder looks like these:</p>
  
  <pre><code>./data
     |-doc
     |---content
     |---template
     |-img
     |---chart
     |---icon
     |---logo
     |---pattern
     |---people
     |---photo
     |---symbol
     |-----brandklassen
     |-----brandschutzzeichen
     |-----gebotszeichen
     |-----gefahrensymbole
     |-----rettungszeichen
     |-----verbotszeichen
     |-----verkehrsrechtzeichen
     |-----warnzeichen
     |---wallpaper
  </code></pre>
  
  <p><code>/data/doc</code> and all subfolders are ok.<br>
  <code>/data/img/chart</code> to <code>/data/img/people</code> are also ok.  </p>
  
  <p>Within <code>/data/img/photo</code> only 14 out of 21 images are copied.<br>
  <code>/data/img/symbol</code> with sub-folders and <code>/data/img/wallpaper</code> were ignored completely.</p>