Set up towncrier for release note management

This copies all the settings from Trio (they seem very reasonable),
and allows for a new release-notes management system that should make
releases easier.

Author: pgjones

CONTRIBUTING.md

@@ -111,6 +111,17 @@ how to get started:
 * [How to contribute to an Open Source Project on GitHub](https://egghead.io/series/how-to-contribute-to-an-open-source-project-on-github)
 
 
+### Release notes
+
+We use towncrier to manage our release notes. Basically, every pull
+request that has a user visible effect should add a short file to the
+newsfragments/ directory describing the change, with a name like
+<ISSUE NUMBER>.<TYPE>.rst. See newsfragments/README.rst for
+details. This way we can keep a good list of changes as we go, which
+makes the release manager happy, which means we get more frequent
+releases, which means your change gets into users’ hands faster.
+
+
 ## After you submit a PR
 
 We'll try to review it promptly and give feedback -- but if you

docs/source/changes.rst

@@ -3,6 +3,8 @@ History of changes
 
 .. currentmodule:: h11
 
+.. towncrier release notes start
+
 v0.9.0 (2019-05-15)
 -------------------
 

newsfragments/.gitkeep

@@ -0,0 +1,27 @@
+This directory collects "newsfragments": short files that each contain
+a snippet of ReST-formatted text that will be added to the next
+release notes. This should be a description of aspects of the change
+(if any) that are relevant to users. (This contrasts with your commit
+message and PR description, which are a description of the change as
+relevant to people working on the code itself.)
+
+Each file should be named like ``<ISSUE>.<TYPE>.rst``, where
+``<ISSUE>`` is an issue numbers, and ``<TYPE>`` is one of:
+
+* ``feature``
+* ``bugfix``
+* ``doc``
+* ``removal``
+* ``misc``
+
+So for example: ``123.feature.rst``, ``456.bugfix.rst``
+
+If your PR fixes an issue, use that number here. If there is no issue,
+then after you submit the PR and get the PR number you can add a
+newsfragment using that instead.
+
+Note that the ``towncrier`` tool will automatically
+reflow your text, so don't try to do any fancy formatting. You can
+install ``towncrier`` and then run ``towncrier --draft`` if you want
+to get a preview of how your change will look in the final release
+notes.

newsfragments/README.rst

@@ -0,0 +1,40 @@
+[tool.towncrier]
+# Usage:
+# - PRs should drop a file like "issuenumber.feature" in newsfragments
+#   (or "bugfix", "doc", "removal", "misc"; misc gets no text, we can
+#    customize this)
+# - At release time after bumping version number, run: towncrier
+#   (or towncrier --draft)
+package = "h11"
+filename = "docs/source/changes.rst"
+directory = "newsfragments"
+underlines = ["-", "~", "^"]
+issue_format = "`#{issue} <https://github.com/python-hyper/h11/issues/{issue}>`__"
+
+# Unfortunately there's no way to simply override
+# tool.towncrier.type.misc.showcontent
+
+[[tool.towncrier.type]]
+directory = "feature"
+name = "Features"
+showcontent = true
+
+[[tool.towncrier.type]]
+directory = "bugfix"
+name = "Bugfixes"
+showcontent = true
+
+[[tool.towncrier.type]]
+directory = "doc"
+name = "Improved Documentation"
+showcontent = true
+
+[[tool.towncrier.type]]
+directory = "removal"
+name = "Deprecations and Removals"
+showcontent = true
+
+[[tool.towncrier.type]]
+directory = "misc"
+name = "Miscellaneous internal changes"
+showcontent = true