website: start documenting the command-line

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

+---
+layout: "docs"
+---
+
+# Packer Command-Line
+
+Packer is controlled using a command-line interface. All interaction with
+Packer is done via the `packer` tool. Like many other command-line tools,
+the `packer` tool takes a subcommand to execute, and that subcommand may
+have additional options as well. Subcommands are executed with
+`packer SUBCOMMAND`, where "SUBCOMMAND" is obviously the actual command you wish
+to execute.
+
+If you run `packer` by itself, help will be displayed showing all available
+subcommands and a brief synopsis of what they do. In addition to this, you can
+run any `packer` command with the `-h` flag to output more detailed help for
+a specific subcommand.
+
+In addition to the documentation available on the command-line, each command
+is documented on this website. You can find the documentation for a specific
+subcommand using the navigation to the left.

website/source/layouts/docs.erb

@@ -31,7 +31,7 @@
 							<li><a href="/docs/basics/terminology.html">Terminology</a></li>
 
 							<li class="nav-header">Command-Line</li>
-							<li><a href="#">Introduction</a></li>
+							<li><a href="/docs/command-line/introduction.html">Introduction</a></li>
 							<li><a href="#">Build</a></li>
 							<li><a href="#">Validate</a></li>