forces a .gz extension on all
files so that
will not compress them twice.
This can be useful for files with names truncated after a file transfer.
On systems with a 14 char limitation on file names, the original name
is truncated to make room for the .gz suffix. For example,
12345678901234 is renamed to 12345678901.gz. A file name such as foo.tgz
is left intact.