Git: Revert to Old Version
Revert a File
git checkout -- filename
This will update the file filename in working directory. It'll be from your local repository. Effectively, revert whatever you've done to the file.
Revert a Directory
git checkout HEAD -- dirFullPath
This will update the dir dirFullPath to the commit version in HEAD. (typically the last commit.) Replace HEAD by a commit hash to revert to other version.
Revert a File to Last Commit
# revert file to last commit git checkout HEAD -- filename
# revert file to the commit before last commit git checkout HEAD^ -- filename
Revert a File to Specific Commit
# revert a file of specific commit git checkout b9d6f -- filename
git log to find the commit id.
[see Git: View History/Log]