title: gdal_merge not recognized as internal or external command in OSGeo4W
body: <p>I've just installed OSGeo4W and am trying to run gdal_merge from the OSGeo4W Shell from a directory other than C.</p>
  
  <pre><code>gdal_merge.py -o output.tif -a_nodata 0 1.tif 2.tif
  </code></pre>
  
  <p>I also tried: <code>gdal_merge -o output.tif -a_nodata 0 1.tif 2.tif</code></p>
  
  <p>I receive the following error: </p>
  
  <blockquote>
    <p>gdal_merge is not recognized as an internal or external command.</p>
  </blockquote>
  
  <p>I checked several directories in C:\OSGeo4W and I found gdal_merge.py is in C:\OSGeo4W\apps\Python37\Scripts. Do I need to duplicate the .py folder somewhere else? Thanks for your help. I thought gdal_merge should be included in the list of shell commands.</p>