Rollback File to much earlier version

git diff <commit hash> <filename>

git reset <commit hash> <filename>

git checkout <commit hash>
git checkout -b <new branch name>

git checkout <my branch>
git rebase master
git checkout master
git merge <my branch>

$ git checkout $A file

$ git revert $B

git checkout <my branch>
git rebase master
git checkout master
git merge <my branch>

---o----o----o----o  master
    ---A----B       <my branch>

git rebase master <my branch>

---o----o----o----o   master
                   ----A'----B'  <my branch>

git checkout master
git merge <my branch>

---o----o----o----o----A'----B'  master, <my branch>

git branch -d <my branch>

git revert <hash>

git checkout <commit hash> file

git commit -a