This might become an RFC.
In Mir we reasonably often have a situation where, in order to get some feature work done, we must first do a bunch of other, semi-related feature work first. To make reviewing (and later bisecting) easier, we tend to make these a bunch of different branches and have PRs with the base-branch set like so:
master -> A -> B -> C -> …
This works OK, except that if you have bors set to delete merged branches then after
A is bors-ed and merged into master the base-branch of B is deleted, which irrecovably closes the
It would be nice if (and it seems that GitHub exposes enough API to) bors would merge
A, change the base branch of
B to master, and then delete
As an extra bit of ergonomics, it would be even better if
bors r+ on the dependent branches would be deferred until the base branch was master - so given the PR stack
A -> B -> C -> D you could review B and have
A -> B (bors r+) -> C -> D and it would wait there until
A was merged, then it would also merge B.