The version number of wattsi is built upstream by counting the number of
commits of the master branch.

To have the same version number in the binary package and the binary itself in
Debian, we compute the version number at the time we import the new orig tar
when invoking uscan.

The script debian/set_version.sh does this and stores the value in
debian/wattsi.version.

For this to work, we must have the remote upstream repo in the repo of the
debian package. Do like this:

  git remote add upstream https://github.com/whatwg/wattsi

You also need a rather recent version of uscan >= 2.26.6 (2.25.15 won't work)
