Updates to hacking howto

* adds "what's where" section which isn't wildly interesting right now
  but it's somewhat interesting
* adds "wiping environment" section

docs/hackinghowto.rst

@@ -41,7 +41,8 @@ If you're running Debian GNU/Linux or a Debian-derived distribution
 such as Mint or Ubuntu, running the following should install these
 requirements::
 
-    sudo apt-get install mongodb git-core python python-dev python-lxml
+    sudo apt-get install mongodb git-core python python-dev \
+         python-lxml
 
 
 Running bootstrap and buildout
@@ -78,11 +79,26 @@ Updating dependencies
 ---------------------
 
 While hacking on GNU MediaGoblin over time, you'll eventually have to
-update the dependencies.  To do that, run::
+update your development environment.  To do that, run::
 
     ./bin/buildout
 
 
+Wiping your environment for a clean-slate
+-----------------------------------------
+
+Delete the following directories:
+
+* bin/
+* develop-eggs/
+* eggs/
+* mediagoblin.egg-info/
+* parts/
+* user_dev/
+
+FIXME - how to drop data from mongodb?
+
+
 Running the server
 ==================
 
@@ -99,6 +115,32 @@ Run::
     ./bin/nosetests
 
 
+What's where
+============
+
+After you've run buildout, you're faced with the following directory
+tree::
+
+    mediagoblin/
+    |- mediagoblin/              source code
+    |  |- tests/
+    |  |- templates/
+    |  |- auth/
+    |  \- submit/
+    |- docs/                     documentation
+    |
+    |        the rest of these directories are generated by
+    |        buildout.
+    |
+    |- bin/                      scripts
+    |- develop-eggs/
+    |- eggs/
+    |- mediagoblin.egg-info/
+    |- parts/
+    |- user_dev/                 sessions, etc
+
+
+
 Quickstart for Django programmers
 =================================