Git's rerere is immensely useful. However, if you erroneously
record a wrong conflict resolution, it's not entirely clear how to
delete it again. The preimage file is stored under
$GIT_DIR/rr-cache/some-sha1-sum/preimage, which is not a convenient
place to look for that one wrong resolution if you have hundreds of
them. ;-)
However, v1.6.6-9-gdea4562 introduced rerere's forget subcommand,
which was not documented until recently (v1.7.1.1-2-g2c64034). So
when rerere replays a wrong resolution onto your file, simply use git
rerere forget path/to/file to forget the wrong resolution.
To (temporarily) replace the resolved version with the originial
version containing conflict markers, use git checkout -m --
path/to/file. You can then issue a git rerere to replay the
resolution again.