And for those curious, this will enable us to share repositories between
all of the work done on a given slave -- which means we'll avoid doing
full clones in 99% of cases and in particular, it will save us 5-10
minutes on every try build we do as well as greatly lowering the load on
hg.mozilla.org.
We've got other work to do before we can flip this on, but this was part #1.