changelog: update ahead of 0.86 release

CHANGELOG.rst

@@ -2,7 +2,27 @@
 master (unreleased)
 --------------------
 
-- Various doc improvements.
+v0.86.1
+--------
+
+- Update RocksDB to 6.7.3, and Go to 1.14.2, along with many other package dependencies.
+- The ``etcdtest`` package no longer embeds an Etcd server. Instead, an ``etcd``
+ binary *must* be available on the PATH and is invoked as a sub-process,
+ using Unix domain sockets. Users who use ``etcdtest`` themselves, or are running
+ Gazette tests outside of the hermetic Docker build environment, must provide a
+ reasonably recent version of ``etcd``.
+- Relatedly, the gazette client_ package no longer depends on Etcd (including the Etcd client).
+- JSON-framed messages are now able to use custom marshal/demarshal routines.
+- ``gazctl journals/shards apply`` now interprets revision ``-1`` (previously
+ disallowed) to mean "don't care", allowing specs to be applied which will always
+ overwrite what's in Etcd.
+ This makes sense for specs managed in another source-of-truth (eg, git).
+- Mitigations and improved logging for issue GH-248_.
+- Remove explicit TCP keep-alive management, as this is now Go default.
+- Various doc improvements & cleanups.
+
+.. _GH-248: GH-248
+.. _client: https://godoc.org/go.gazette.dev/core/broker/client
 
 v0.85.2
 --------