$ mkdir git-example
$ cd git-example
$ git init
Initialized empty Git repository in /Users/grahambleach/git-example/.git/
$ echo "This is a test repo" > README
$ git add README
$ git commit
[master (root-commit) b8fd413] This is a test
 1 file changed, 1 insertion(+)
 create mode 100644 README
$ echo 'Oh no, it is not!' >> README
$ git add README
$ git commit
[master dfd464c] Dummy
 1 file changed, 1 insertion(+)
$ git revert dfd464c
[master 887e21f] Revert "Dummy"
 1 file changed, 1 deletion(-)
$ cat README
This is a test repo
$