[atsjie]

This.

All teams I've worked for in the last few years basically did this.

Although we never distinguished between features/topics explicitly, the proces would be the same.

Having one branch per story is just very simple from a management perspective; it aligns user requirements, graphics design, development, code review and deployment into one trackable unit.

Stories are never too large so in practice code branches don't exist for too long, a couple of days usually. If two or more developers work on the same story they'll use the same branch. If two stories are code-wise interdependent they'll reuse each other's branches as they see fit.