+dit(bf(--partial-dir=DIR)) Turns on --partial mode, but tells rsync to
+put a partially transferred file into DIR instead of writing out the
+file to the destination dir. Rsync will also use a file found in this
+dir as data to speed up the transfer (i.e. when you redo the send after
+rsync creates a partial file) and delete such a file after it has served
+its purpose.
+
+Rsync will create the dir if it is missing (just the last dir -- not the
+whole path). This makes it easy to use a relative path (such as
+"--partial-dir=.rsync-partial") to have rsync create the partial-directory
+in the destination file's directory (rsync will also try to remove the DIR
+if a partial file was found to exist at the start of the transfer and the
+DIR was specified as a relative path).
+
+If you are deleting files on the destination and your partial-dir is
+inside the destination hierarchy, make sure you specify an exclude to
+prevent the partial file from being deleted (it could get deleted at the
+end of the transfer when using --delete-after, or at the beginning of the
+transfer when using --delete). E.g. "--exclude=.rsync-partial/".
+
+IMPORTANT: the --partial-dir should not be writable by other users to
+avoid a security risk. E.g. AVOID "/tmp".
+