A lot of times, we do an upgrade operation which does not touches all the parts
of the stores. But right not, we have a blind logic which processes everything.
To selectively upgrade parts of repository, we need to persist existing data
which is untouched.
However while creating current repository backup, we rename the whole store
leaving no option to persist untouched files.
We switch to copy+delete so that we can only delete data files which are changed
by the operation and leave rest untouched.