When the minor-mode clean-kill-ring-mode is enabled, any string that
satisfies one of the filter predicates in the clean-kill-ring-filters list
variable will not be allowed into the kill-ring.
By default clean-kill-ring-filters only contains the predicate
string-blank-p, which means that no blank lines will be allowed into the
kill-ring.
If the variable clean-kill-ring-prevent-duplicates is set to a non-nil value
then upon killing text that already exists in kill-ring, the old duplicate
entries will be removed.
To manually clean the kill-ring, call the interactive function
clean-kill-ring-clean.
This library is available on MELPA.
MIT