I don't know why we're getting index.lock errors but they're impossile to stop
anyway given that other processes can be calling git commands. So we're retrying
a few times before re-raising. To do this we need to clone the command and the current
implementation for that is best-effort.
I do worry about the maintainability of that but we'll see how it goes.
Also, I thought you'd need to clone the task (if it exists) but now I think not;
as long as you don't call done twice on it you should be fine, and you shouldn't
be done'ing a task as part of running a command: that should happen higher up.