Restart/undo conflict resolution in a single file

Question

In a larger git merge with several conflicting files, I incorrectly marked a file as resolved (using git add FILE after some editing)

Now I\'d like to u

Answer 1

git reset HEAD FILE

Example

$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)

Answer 2

Found the solution here: http://gitster.livejournal.com/43665.html

git checkout -m FILE

This restores the unresolved state, including all information about parent and merge base, which allows restarting the resolution.