title: Concatenate netcdf files with multiple 'record' dimensions
body: <p>Let's consider those two files:</p>
  
  <pre><code>from netCDF4 import Dataset as dset
  
  for i in range(2):
       with dset('test_{}.nc'.format(i),'w') as f:
           f.createDimension('A',5)
           f.createDimension('B',8)
           f.createVariable('v1',float,('A',))
           f.createVariable('v2',float,('B',))
           f['v1'][:] = range(i*5,i*5+5)
           f['v2'][:] = range(i*8,i*8+8)
  </code></pre>
  
  <p>If the two dimensions are unlimited ncrcat works directly and concatenate v2 along B and v1 along A.</p>
  
  <pre><code>ncrcat test_0.nc test_1.nc test_01.nc
  </code></pre>
  
  <p>However if the dimensions are fixed size like in the example above I have to successively set A and B as record dimension to make them unlimited and then concatenate</p>
  
  <pre><code>ncks --mk_rec_dmn A test_0.nc test_0u.nc ; mv test_0u.nc test_0.nc
  ncks --mk_rec_dmn B test_0.nc test_0u.nc ; mv test_0u.nc test_0.nc
  ncks --mk_rec_dmn A test_1.nc test_1u.nc ; mv test_1u.nc test_1.nc
  ncks --mk_rec_dmn B test_1.nc test_1u.nc ; mv test_1u.nc test_1.nc
  ncrcat test_0.nc test_1.nc test_01.nc
  </code></pre>
  
  <p>Is there another way to do this with less lines? </p>