* Add separate clone parameter
This brings the hg module in line with the git module for controlling
individual update and checkout functionality based on whether the
directory exists or not.
It also allows specifying `no` for both to pull the remote revision
without performing a checkout
* Reflect the right added ver for the hg clone arg
The command `hg up -C` by default moves to the latest revision on the
current branch. The `discard` function was trying to update to a
different branch, in case it was provided, by passing a `-r REVISION`
argument. Not only is this not the intended effect of the `discard`
function, but this also could update to a different branch that hasn't
been pulled yet, which is how we were experiencing trouble.
Instead, we unconditionally do `hg up -C -r .` to "update" to the
current revision (i.e. to "."), while `-C/--clean`ing the current
directory. This is similar to `hg revert --all`, except that it also
undoes the merge state of the working directory, in case there was
any.
