I've seen this demonstrated before in various screencasts and can't find it searching through the docs. I do use helm-swoop-edit quite often in a single buffer but when I need to change all occurrences across a project it gets a bit tedious.

For bonus points if there is a utility function to build such a buffer from helm results? I'd be very interested as my general project searching methods are helm-git-grep, helm-do-grep and helm-do-ag.