Write up a simple release guide

doc/release.md

@@ -0,0 +1,28 @@
+# Release checklist
+
+1.  First check if we can build against against all the newest dependencies.  If
+    that's not the case, it's probably a good idea to first make a separate
+    commit to bump the dependency upper bounds (and test it).
+
+2.  Write up the `CHANGELOG`.  You can inspect the log of what changed by doing
+    something like:
+
+        git log A.B.C.D..
+
+    Where `A.B.C.D` is the old version.
+
+3.  Now figure out whether this is a minor or major version bump.  Follow the
+    [PVP](https://pvp.haskell.org/) guidelines.  Assume the new version is
+    `E.F.G.H`.
+
+4.  Create a commit with the message `Bump version to E.F.G.H`.  This commit
+    should only change two things:
+
+    - The version number in the `.cabal` file
+    - The top of the `CHANGELOG`
+
+4.  Create a tarball using `cabal sdist` and upload this to Hackage.  If the
+    upload succeeds, create an annotated git tag:
+
+        git tag -am E.F.G.H{,}
+        git push --tags