Our initial suggestion was to do something along the lines of your proposal. But we found that when we ask an agent to implement features for `t-n`^th PR, even when we are overly specific makes the code rather divergent, to the point that sometimes the `t-n+1`th task description doesn't really make a lot of sense.
In fact, there are some papers (that we cited) which create a set of tasks doing exactly this, and it is non-trivial [1].