website: document the fix command

website/source/docs/command-line/fix.html.markdown

+---
+layout: "docs"
+page_title: "Command-line: Fix"
+---
+
+# Command-Line: Fix
+
+The `packer fix` command takes a template and finds backwards incompatible
+parts of it and brings it up to date so it can be used with the latest version
+of Packer. After you update to a new Packer release, you should run the
+fix command to make sure your templates work with the new release.
+
+The fix command will output the changed template to standard out, so you
+should redirect standard using standard OS-specific techniques if you want to
+save it to a file. For example, on Linux systems, you may want to do this:
+
+```
+$ packer fix old.json > new.json
+```
+
+If fixing fails for any reason, the fix command will exit with a non-zero
+exit status. Error messages appear on standard error, so if you're redirecting
+output, you'll still see error messages.
+
+<div class="alert alert-block alert-info">
+<strong>Even when Packer fix doesn't do anything</strong> to the template,
+the template will be outputted to standard out. Things such as configuration
+key ordering and indentation may be changed. The output format however, is
+pretty-printed for human readability.
+</div>
+
+The full list of fixes that the fix command performs is visible in the
+help output, which can be seen via `packer fix -h`.

website/source/layouts/docs.erb

@@ -11,6 +11,7 @@
 			<li><h4>Command-Line</h4></li>
 			<li><a href="/docs/command-line/introduction.html">Introduction</a></li>
 			<li><a href="/docs/command-line/build.html">Build</a></li>
+			<li><a href="/docs/command-line/fix.html">Fix</a></li>
 			<li><a href="/docs/command-line/validate.html">Validate</a></li>
 		</ul>