[gdal-dev] gdalwarp -dstalpha does not create alpha band

[Jack Glendening]

For gdalwarp (GDAL 2.3.1), using -dstalpha (hoping to get transparent
pixels outside the original image area) ala 

 gdalwarp -dstalpha -srcnodata 0 -t_srs EPSG:4326 in.tif out.tif 

for an input geotiff RGB image (created by gdal_translate) I get an RGB
output image, not an RGBA as I expected. From googling, it appears
-dstalpha works for others. This seems so simple, cannot understand
what could be going wrong.

Jack