isMutating re-render for every concat mutation

[Maxime]

Because between each mutation there is a "success" followed by a "pending" the value switch from 0 to 1 in one tick which cause a re-render.

I am wondering if there is a way to avoid the value 0 since as soon as the first mutation finish we start the second one.

Maybe we should update the sate of next mutation before we finish the previous one or update at the same time.

This is not a bug.