Added --keep option to export:
--keep KEEP_PATH
When used with --cleanup, prevents file or directory KEEP_PATH from being
deleted when cleanup is run. Use this if there are files in the export
directory that you don't want to be deleted when --cleanup is run. KEEP_PATH
may be a file path, e.g. '/Volumes/Photos/keep.jpg',
or a file path and wild card, e.g. '/Volumes/Photos/*.txt', or a directory,
e.g. '/Volumes/Photos/KeepMe'. KEEP_PATH may be an absolute path or a
relative path. If it is relative, it must be relative to the export
destination. For example if export destination is /Volumes/Photos and you
want to keep all .txt files, you can specify
--keep "/Volumes/Photos/*.txt" or --keep "*.txt". If wild card is used,
KEEP_PATH must be enclosed in quotes to prevent the shell from expanding the
wildcard, e.g. --keep "/Volumes/Photos/*.txt". If KEEP_PATH is a
directory, all files and directories contained in KEEP_PATH will be kept.
--keep may be repeated to keep additional files/directories.