Refactoring and feature additions should be in separate commits. This allows the definition of refactoring as a "behaviour preserving transformation" to be useful in a practical way beyond the immediate point of use - it's helpful information to have while regressing to find the source of a bug, for instance. If the refactoring is mixed with other changes it becomes much less useful.

Ideally, I'd like refactoring tools in IDEs to work with version control to check in and revert as I refactor/undo - and potentially even branch when I start refactoring then merge when I'm done and the tests pass.

Refactoring and feature additions should be in separate commits. This allows the definition of refactoring as a "behaviour preserving transformation" to be useful in a practical way beyond the immediate point of use - it's helpful information to have while regressing to find the source of a bug, for instance. If the refactoring is mixed with other changes it becomes much less useful.

Ideally, I'd like refactoring tools in IDEs to work with version control to check in and revert as I refactor/undo.