I believe that you are applying the
This option instructs rsync to use DIR on the destination machine as an additional
hierarchy to compare destination files against doing transfers (if the files are
missing in the destination directory). If a file is found in DIR that is identical
to the sender’s file, the file will NOT be transferred to the destination direc‐
tory. This is useful for creating a sparse backup of just files that have changed
from an earlier backup. This option is typically used to copy into an empty (or
newly created) directory.
Beginning in version 2.6.4, multiple --compare-dest directories may be provided,
which will cause rsync to search the list in the order specified for an exact
match. If a match is found that differs only in attributes, a local copy is made
and the attributes updated. If a match is not found, a basis file from one of the
DIRs will be selected to try to speed up the transfer.
If DIR is a relative path, it is relative to the destination directory. See also
--copy-dest and --link-dest.
NOTE: beginning with version 3.1.0, rsync will remove a file from a non-empty des‐
tination hierarchy if an exact match is found in one of the compare-dest hierar‐
chies (making the end result more closely match a fresh copy).
If I am reading this correctly,
--compare-dest used used to stop the sending certain files. This would allow you to create a new copy destination directory, containing only files that have changed since the last copy. Sort of an incremental copy, if you will.