The DLFP backend doesn't get object older than 60 days: we don't
have to store older "seen" value in the storage.
Bad news: we have to store the date of the object to perform
the cleanup. It will increase the storage size (before a big
improvement).
Since we didn't store date value before this commit, this feature
will work 60 days after module upgrade.
This reverts commit 4a5456b152.
This commit was here to bypass a bug of dlfp rss Atom.
The bug is fixed and the commit can be reverted.
Reference : http://linuxfr.org/suivi/855
It is unused, and no backend implemented it — so it was wrong to have it
in the function signature.
It also does not seem very helpful, we have get_threads() if we want to
do something advanced with treads.
fixes#825
