rsync(1) --delete
a fast, versatile, remote (and local) file-copying tool
--delete
       This tells rsync to delete extraneous files from the receiving  side  (ones  that  aren’t  on  the
       sending  side),  but  only  for  the directories that are being synchronized.  You must have asked
       rsync to send the whole directory (e.g.  "dir"  or  "dir/")  without  using  a  wildcard  for  the
       directory’s  contents  (e.g.  "dir/*")  since the wildcard is expanded by the shell and rsync thus
       gets a request to transfer individual files, not the files’  parent  directory.   Files  that  are
       excluded   from   the   transfer  are  also  excluded  from  being  deleted  unless  you  use  the
       --delete-excluded option or mark the  rules  as  only  matching  on  the  sending  side  (see  the
       include/exclude modifiers in the FILTER RULES section).

              Prior  to rsync 2.6.7, this option would have no effect unless --recursive was enabled.  Beginning
              with 2.6.7, deletions will also occur when --dirs (-d) is enabled, but only for directories  whose
              contents are being copied.

              This option can be dangerous if used incorrectly!  It is a very good idea to first try a run using
              the --dry-run option (-n) to see what files are going to be deleted.

              If the sending side detects any I/O errors, then the deletion of any files at the destination will
              be  automatically  disabled. This is to prevent temporary filesystem failures (such as NFS errors)
              on the sending side from causing a massive deletion of files on the destination.  You can override
              this with the --ignore-errors option.

              The  --delete  option  may  be combined with one of the --delete-WHEN options without conflict, as
              well as --delete-excluded.  However, if none of the --delete-WHEN  options  are  specified,  rsync
              will  choose  the  --delete-during  algorithm  when  talking  to  rsync  3.0.0  or  newer, and the
              --delete-before  algorithm  when  talking  to  an  older  rsync.   See  also  --delete-delay   and
              --delete-after.
source manpages: rsync