User stories for git-extract

@charlierudolph @allewun adding user stories that describe end-user value
Look at one of the conversations about one of the outdated diffs. You thought that sounded better, but only updated the without_open_changes. You then looked at the with_open_changes. (This is why I hate having this stuff in here. There is too much repetition).

My versions mentions so the `issue can be reviewed separately` which is how git-extract is making your code reviews more efficient.