doc: Minor tweaks

doc/overview.xml

@@ -79,9 +79,10 @@
       and <emphasis>predictable</emphasis>.
     </para>
     <para>
-      But unlike many default image-based deployments, OSTree
-      supports a persistent, writable <literal>/etc</literal> that
-      is preserved across upgrades.
+      But unlike many default image-based deployments, OSTree supports
+      exactly two persistent writable directories that are preserved
+      across upgrades: <literal>/etc</literal> and
+      <literal>/var</literal>.
     </para>
     <para>
       Because OSTree operates at the Unix filesystem layer, it works

doc/repo.xml

@@ -8,9 +8,9 @@
   <chapter id="repository-intro">
     <title>Core object types and data model</title>
     <para>
-      OSTree is deeply inspired by git; like git, OSTree is a
-      userspace versioning filesystem.  It is worth taking some time
-      to familiarize yourself with <ulink
+      OSTree is deeply inspired by git; the core layer is a userspace
+      content-addressed versioning filesystem.  It is worth taking
+      some time to familiarize yourself with <ulink
       url="http://git-scm.com/book/en/Git-Internals">Git
       Internals</ulink>, as this section will assume some knowledge of
       how git works.