How can I reset or revert a file to a specific revision?

Question

I have made some changes to a file which has been committed a few times as part of a group of files, but now want to reset/revert the changes on it back to a previous versio

Answer 1

git checkout ref|commitHash -- filePath

e.g.

git checkout HEAD~5 -- foo.bar
or 
git checkout 048ee28 -- foo.bar