directory permissions
       ‐‐acls, ‐A               preserve ACLs (implies ‐‐perms)
       ‐‐xattrs, ‐X             preserve extended attributes
       ‐‐owner, ‐o              preserve owner (super‐user only)
       ‐‐group, ‐g              preserve group
       ‐‐devices                preserve device files (super‐user only)
       ‐‐copy‐devices           copy device contents as a regular file
       ‐‐write‐devices          write to devices as files (implies ‐‐inplace)
       ‐‐specials               preserve special files
       ‐D                       same as ‐‐devices ‐‐specials
       ‐‐times, ‐t              preserve modification times
       ‐‐atimes, ‐U             preserve access (use) times
       ‐‐open‐noatime           avoid changing the atime on opened files
       ‐‐crtimes, ‐N            preserve create times (newness)
       ‐‐omit‐dir‐times, ‐O     omit directories from ‐‐times
       ‐‐omit‐link‐times, ‐J    omit symlinks from ‐‐times
       ‐‐super                  receiver attempts super‐user activities
       ‐‐fake‐super             store/recover privileged attrs using xattrs
       ‐‐sparse, ‐S             turn sequences of nulls into sparse blocks
       ‐‐preallocate            allocate dest files before writing them
       ‐‐dry‐run, ‐n            perform a trial run with no changes made
       ‐‐whole‐file, ‐W         copy files whole (w/o delta‐xfer algorithm)
       ‐‐checksum‐choice=STR    choose the checksum algorithm (aka ‐‐cc)
       ‐‐one‐file‐system, ‐x    don’t cross filesystem boundaries
       ‐‐block‐size=SIZE, ‐B    force a fixed checksum block‐size
       ‐‐rsh=COMMAND, ‐e        specify the remote shell to use
       ‐‐rsync‐path=PROGRAM     specify the rsync to run on remote machine
       ‐‐existing               skip creating new files on receiver
       ‐‐ignore‐existing        skip updating files that exist on receiver
       ‐‐remove‐source‐files    sender removes synchronized files (non‐dir)
       ‐‐del                    an alias for ‐‐delete‐during
       ‐‐delete                 delete extraneous files from dest dirs
       ‐‐delete‐before          receiver deletes before xfer, not during
       ‐‐delete‐during          receiver deletes during the transfer
       ‐‐delete‐delay           find deletions during, delete after
       ‐‐delete‐after           receiver deletes after transfer, not during
       ‐‐delete‐excluded        also delete excluded files from dest dirs
       ‐‐ignore‐missing‐args    ignore missing source args without error
       ‐‐delete‐missing‐args    delete missing source args from destination
       ‐‐ignore‐errors          delete even if there are I/O errors
       ‐‐force                  force deletion of dirs even if not empty
       ‐‐max‐delete=NUM         don’t delete more than NUM files
       ‐‐max‐size=SIZE          don’t transfer any file larger than SIZE
       ‐‐min‐size=SIZE          don’t transfer any file smaller than SIZE
       ‐‐max‐alloc=SIZE         change a limit relating to memory alloc
       ‐‐partial                keep partially transferred files
       ‐‐partial‐dir=DIR        put a partially transferred file into DIR
       ‐‐delay‐updates          put all updated files into place at end
       ‐‐prune‐empty‐dirs, ‐m   prune empty directory chains from file‐list
       ‐‐numeric‐ids            don’t map uid/gid values by user/group name
       ‐‐usermap=STRING         custom username mapping
       ‐‐groupmap=STRING        custom groupname mapping
       ‐‐chown=USER:GROUP       simple username/groupname mapping
       ‐‐timeout=SECONDS        set I/O timeout in seconds
       ‐‐contimeout=SECONDS     set daemon connection timeout in seconds
       ‐‐ignore‐times, ‐I       don’t skip files that match size and time
       ‐‐size‐only              skip files that match in size
       ‐‐modify‐window=NUM, ‐@  set the accuracy for mod‐time comparisons
       ‐‐temp‐dir=DIR, ‐T       create temporary files in directory DIR