Added documentation on update strategy. Fix all navs in this section.

www/data/docs_sidebar.yml

@@ -49,6 +49,8 @@ sidebar_links:
       link: "/docs/run-packages-security/"
     - title: Topologies
       link: "/docs/run-packages-topologies/"
+    - title: Update Strategy
+      link: "/docs/run-packages-update-strategy/"
     - title: Run multiple packages
       link: "/docs/run-packages-director/"
   - title: Habitat internals

www/source/docs/run-packages-update-strategy.html.md

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+---
+title: Update Strategy
+---
+
+# Update Strategy
+
+The Habitat supervisor can be configured to implement an optional _update strategy_, which describes how the supervisor and its peers within a service group should respond when a new version of a package is available.
+
+To use an update strategy, the supervisor be configured to watch a [depot](/docs/concepts-depot) for new versions. Habitat provides a public depot, but you can also run one inside your own datacenter using the `core/hab-depot` package.
+
+## Configuring an Update Strategy
+
+The current version of Habitat supports only one update strategy: `at-once`. This strategy does no peer coordination with other supervisors in the service group; it merely updates the underlying Habitat package whenever it detects that a new version has been published to a depot.
+
+To start a supervisor with the auto-update strategy, pass the `--strategy` argument to a supervisor start command, and optionally specify the depot URL:
+
+       hab start yourorigin/yourapp --strategy at-once --url https://willem.habitat.sh/v1/depot
+
+## Configuring an Update Strategy with a Depot View
+
+A _view_ in a depot is a point-in-time snapshot of the state of the depot. In point of fact, it is a [materialized view](https://en.wikipedia.org/wiki/Materialized_view) of the depot, starting with the specific `origin/package/version/release` quad, and encapsulating all of the transitive dependencies of that quad. This is very useful for continuous deployment purposes:
+
+* By convention, you name the view in the depot after the name of your service group (e.g. `myapp.production`)
+* You deliver new versions of `myapp` as Habitat packages to the depot
+* When you are ready to roll out a new version of the application, you update the view corresponding to the intended environment
+* The supervisors in that service group, configured with an appropriate update strategy, update their underlying Habitat package, optionally coordinating with one another, and restart the service.
+
+Configuring the supervisors'  update strategy URL to point to a view ensures that new versions of the application do not get deployed until the view is updated, thereby preventing unstable versions from reaching environments for which they are not intended.
+
+To start a supervisor with a strategy and pointing to a view, modify slightly the URL to the depot:
+
+       hab start yourorigin/yourapp --strategy at-once --url https://yourdepot.example.com/v1/depot/views/yourview
+
+`yourview` represents the view you have created in the depot.
+
+_At the moment, the `hab` command-line tool lacks the ability to create and manage views. To use views, you must run your own depot server and use the internal depot maintenance tool to manage views_.
+
+<hr>
+<ul class="main-content--link-nav">
+  <li>Continue to the next topic</li>
+  <li><a href="/docs/run-packages-director">Run multiple packages</a></li>
+</ul>