Reinstalling packages with missing/corrupt files

Following an unclean shutdown and a colourful fsck, a whole bunch of files have gone missing. The output of ‘rpm -Va’ is several hundred lines long (mostly missing files but also some checksum and other mismatches). Is there an easy way to reinstall packages which have missing and/or corrupt files?

How to pin a package in dnf (Fedora)

I’ve got a temporary situation where I’m working with pre-release F27, and need to keep one package to a specific (working) version and not be upgraded until the subsequent versions stop breaking something. I know in general “you don’t really want to do this”, but as I said, it’s a temporary dealing with a pre-rel system. You can “pin” packages with the apt system, but I can’t locate anything equivalent for dnf.