Update RELEASING documentation

RELEASING

@@ -1,20 +1,14 @@
 Release Checklist
 -----------------------------------------
-[ ] Update __version__ string
-[ ] Update classifiers in setup.py to include the latest supported Python
+[ ] Update classifiers in setup.cfg to include the latest supported Python
     versions.
 [ ] Update the metadata in zonefile_metadata.json to include the latest tzdata
     release from https://www.iana.org/time-zones.
 [ ] If necessary, update the tzdata mirror at https://github.com/dateutil/tzdata
-[ ] Update NEWS with list of changes, giving credit to contributors.
-[ ] Build the source distribution as, at a minimum, .tar.gz and .zip
-[ ] Verify that the source distribution contains all necessary components.
-[ ] Build the binary distribution as a wheel
-[ ] Verify that the binary distribution can be installed and works.
-[ ] Generate MD5 hashes for the source and binary distributions
-[ ] Sign the source and binary distributions with a GPG key (if not the one
-    that made the release, then one signed by the one that made the last
-    release)
+[ ] Update NEWS with list of changes:
+    [ ] Invoke `tox -e towncrier -- --version <NEXT_VERSION>`
+    [ ] Make sure that only `template.rst` remains in changelog.d/
+    [ ] Manually clean up the new NEWS file and then check it in.
 [ ] Commit the changes in git and make a pull request.
 [ ] Accept the pull request and tag the repository with the release number.
 [ ] Add the contents of the NEWS file to the github release notes for the
@@ -36,60 +30,34 @@ for more details.
 
 Versioning
 ----------
-Try and keep to a semantic versioning scheme (http://semver.org/).
+Try and keep to a semantic versioning scheme (http://semver.org/). The versions
+are managed with setuptools_scm, so to update the version, simply tag the
+relevant commit with the new version number.
 
 
-Source releases
-----------
-Release the sources with, at a minimum, .tar.gz and .zip. Make sure you have a
-relatively recent version of setuptools when making the source distribution, as
-earlier version will not include the tests. Other formats are
-optional. They can be generated using:
-
-    python setup.py sdist --formats=zip,gztar
-
-To verify that a source release is correct, inspect it using whatever archive
-utility you have and make sure it contains all the modules and the tests. Also
-make sure that the zoneinfo file is included in the You
-may also want to generate a new clean virtualenv and run the tests from the
-source distribution (python setup.py test).
-
-
-Binary releases
-----------
-It should always be possible to generate a universal wheel binary distribution
-for each release. Generally we do not generate .egg files. In order to generate
-a wheel, you need the wheel package (https://wheel.readthedocs.io/en/latest/)
-installed, which can be installed with:
-
-    pip install wheel
-
-Once this is done, generate the wheel with:
-
-    python setup.py bdist_wheel
-
-
-Signing and generate checksums
-----------
-Since all the outputs are generated in the dist/ directory, can generate all the
-md5 checksums at once from the base directory by executing:
-
-    md5sum dist/*
-
-Save these for when uploading the files. Following this, go into the dist
-directory and sign each of the results with the relevant key:
+Building and Releasing
+----------------------
+Building and releasing can be done using the `release.py` script, which
+automates building, signing and uploading. Since it uses GPG for signing and
+for decrypting a stored token, it requires that `gpg` be installed on your
+system. Because it has python dependencies, the best way to use the
+`release.py` script is to invoke it using `tox`. To build the source and binary
+distributions, use:
 
-    gpg --armor --output <fname>.asc --detach-sig <fname>
+    tox -e build
 
-To automate this for all files, you can use the following command:
+This will build and sign the distributions and put them in `dist/`. Once that
+is done, you can release them with:
 
-    for f  in dist/*; do gpg --armor --output $f.asc --detach-sig $f; done
+    tox -e release
 
-Save these .asc files for when uploading to pypi. Before uploading them, verify
-that they are valid signatures:
+If you have the token stored in your `~/.pypirc` file. If you have stored the
+relevant token in an encrypted file, use the `--passfile` argument:
 
-    gpg --verify <fname>.asc <fname>
+    tox -e release -- --passfile token.gpg
 
-To do this in bulk, you can use the command:
+The `release` command defaults to uploading to test.pypi.org. To upload to
+pypi.org, use the `--release` flag, so putting it all together, we have:
 
-    for f in $(find ./dist -type f | grep -v '.asc$'); do gpg --verify $f.asc $f; done
+    tox -e build
+    tox -e release -- --passfile token.gpg --release