Author: Ewen Cheslack-Postava <me@ewencp.org>
Reviewers: Gwen Shapira
Closes#2795 from ewencp/release-script and squashes the following commits:
f1d0590 [Ewen Cheslack-Postava] Don't expose promotion to the user since it is not implemented yet.
1a6947a [Ewen Cheslack-Postava] Handle cleanup if there's a failure during generation of release notes.
fa58401 [Ewen Cheslack-Postava] Fix hard-coded uses of trunk
639bcca [Ewen Cheslack-Postava] Try to cleanup after most failures.
a3a7245 [Ewen Cheslack-Postava] Fix SCRIPT_DIR to be an absolute path so git clones against the REPO work when it is also your cwd
de54c97 [Ewen Cheslack-Postava] Load/save preferences in a .release-settings.json file so you don't have to keep entering the same info repeatedly
b559a61 [Ewen Cheslack-Postava] Check that the user doesn't have any oustanding diffs before starting the rest of the script
ff0b330 [Ewen Cheslack-Postava] Store original starting branch to switch back to instead of using a default.
b793562 [Ewen Cheslack-Postava] Use 2.12 instead of specific Scala version so we use the default 2.12 version.
382b7f9 [Ewen Cheslack-Postava] MINOR: Add a release script that helps generate release candidates.
Ewen Cheslack-Postava