duplicate a directory by making a minimal set of changes
mirrordir changes the mirror directory to be an exact replica of the
control directory tree in every possible detail suitable for purposes
of timed backup, locally or over FTP, or over a secure tcp
connection. Files whose modification times or sizes differ are
copied. File permissions, ownerships, modification times, access
times, and sticky bits are duplicated. Devices, pipes, and symbolic
and hard links are duplicated. Files or directories that exist in
the mirror directory that don't exist in the control directory are
deleted. It naturally descends into subdirectories to all their
depths. mirrordir tries to be as efficient as possible by making the
minimal set of changes necessary to mirror the directory.
