Changes to smooth out make_release

Changes to smooth out make_release

1) Make the fake 'HeadURL' into a URL which works with our web repo.
Note that this has 'tags/' hardcoded in, so it only works with true
release branches (e.g. rel_x_y_z) not "working" branches
(e.g. rel_x_y).

2) Change range selector when building log to better exclude commits
from previous releases.

Signed-off-by: Dan Wells <dbw2@calvin.edu>
Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Ben Shum <bshum@biblio.org>