I just started to use the EXIFTool but can't figure out how to copy all meta info from one file to another without destroying the destination file's thumbnail image. Is there any way to do so ?
Save the thumbnail first:
exiftool -b -ThumbnailImage destination_image.jpg > destination_thumbnail.jpg
Then mess with all the metadata (copy from source, write into destination), and meanwhile destroy the destination thumbnail, no problem. E.g.
exiftool -tagsFromFile source_image.jpg -XMP:All= -ThumbnailImage= -m destination_image.jpg
Note that you can do any other metadata manipulation as well.
When you are done, copy back the saved thumbnail:
exiftool '-ThumbnailImage<=destination_thumbnail.jpg' destination_image.jpg