Man page update and changes file for 20667

changes/bug20667

+  o Minor bugfixes (directory downloads):
+    - Download all consensus flavors, descriptors, and authority certificates
+      when FetchUselessDescriptors is set, regardless of whether tor is a
+      directory cache or not.
+      Fixes bug 20667; bugfix on all recent tor versions.

doc/tor.1.txt

@@ -504,11 +504,13 @@ GENERAL OPTIONS
     (Default: 1)
 
 [[FetchUselessDescriptors]] **FetchUselessDescriptors** **0**|**1**::
-    If set to 1, Tor will fetch every non-obsolete descriptor from the
-    authorities that it hears about. Otherwise, it will avoid fetching useless
-    descriptors, for example for routers that are not running. This option is
-    useful if you're using the contributed "exitlist" script to enumerate Tor
-    nodes that exit to certain addresses. (Default: 0)
+    If set to 1, Tor will fetch every consensus flavor, descriptor, and
+    certificate that it hears about. Otherwise, it will avoid fetching useless
+    descriptors: flavors that it is not using to build circuits, and authority
+    certificates it does not trust. This option is useful if you're using a
+    tor client with an external parser that uses a full consensus.
+    This option fetches all documents, **DirCache** fetches and serves
+    all documents. (Default: 0)
 
 [[HTTPProxy]] **HTTPProxy** __host__[:__port__]::
     Tor will make all its directory requests through this host:port (or host:80