pull: mark commits from local cache as partial

If one of the localcache repos has the exact same commit we resolved
from the remote, then we need to make sure to mark it as partial so that
we download the full tree.

Closes: #1074

Closes: #1076
Approved by: cgwalters

man/ostree-pull.xml

@@ -78,7 +78,7 @@ Boston, MA 02111-1307, USA.
 
               <listitem><para>
                 Like git's <literal>clone --reference</literal>.  Reuse the provided
-                OSTree repo as a local object cache of objects when doing HTTP fetches.
+                OSTree repo as a local object cache when doing HTTP fetches.
                 May be specified multiple times.
               </para></listitem>
             </varlistentry>