How to Abort Git Bisect

git bisect reset is the correct command. From the documentation:

After a bisect session, to clean up the bisection state and return to the original HEAD, issue the following command:

$ git bisect reset

By default, this will return your tree to the commit that was checked out before git bisect start. (A new git bisect start will also do that, as it cleans up the old bisection state.)