title: .gitignore does not ignore files with certain extensions
body: <p>I added this to my .gitignore file:</p>
  
  <pre><code># JPEG
  *.jpg
  *.jpeg
  *.jpe
  *.jif
  *.jfif
  *.jfi
  
  # JPEG 2000
  *.jp2
  *.j2k
  *.jpf
  *.jpx
  *.jpm
  *.mj2
  
  # JPEG XR
  *.jxr
  *.hdp
  *.wdp
  
  # Graphics Interchange Format
  *.gif
  
  # RAW
  *.raw
  
  # Web P
  *.webp
  
  # Portable Network Graphics
  *.png
  
  # Animated Portable Network Graphics
  *.apng
  
  # Multiple-image Network Graphics
  *.mng
  
  # Tagged Image File Format
  *.tiff
  *.tif
  
  # Scalable Vector Graphics
  *.svg
  *.svgz
  
  # Portable Document Format
  *.pdf
  
  # X BitMap
  *.xbm
  
  # BMP
  *.bmp
  *.dib
  
  # ICO
  *.ico
  
  # 3D Images
  *.3dm
  *.max
  </code></pre>
  
  <p>Found <a href="https://github.com/github/gitignore/blob/master/Global/Images.gitignore" rel="nofollow noreferrer">here</a>.</p>
  
  <p>Then I added some <code>.png</code> files and commited this change and pushed it, but the files are showing up if I execute <code>git status</code>.</p>
  
  <pre><code>    geändert:       skin/frontend/venedor/custom/images/kreis_rot_weiss.png
      geändert:       skin/frontend/venedor/custom/images/kreis_weiss.png
  </code></pre>
  
  <p>What am I doing wrong?</p>