Bugfix: If the UUID of a remote is not known, prevent --from, --to, and other ways of specifying remotes by name from selecting it, since it is not possible to sanely use it.

For example, copy --to such a remote would send the file, but as NoUUID was
its uuid, no location log update was done. And drop --from such a remote
would not do anything, because NoUUID is not listed in the location log..

Remote.hs

@@ -81,7 +81,9 @@ byName' "" = return $ Left "no remote specified"
 byName' n = handle . filter matching <$> remoteList
   where
 	handle [] = Left $ "there is no available git remote named \"" ++ n ++ "\""
-	handle match = Right $ Prelude.head match
+	handle (match:_)
+		| uuid match == NoUUID = Left $ "cannot determine uuid for " ++ name match
+		| otherwise = Right match
 	matching r = n == name r || toUUID n == uuid r
 
 {- Looks up a remote by name (or by UUID, or even by description),

debian/changelog

@@ -20,6 +20,9 @@ git-annex (4.20130228) UNRELEASED; urgency=low
     set to direct mode when it was transferred.
   * webapp: Proceed automatically on from "Configure jabber account"
     to pairing.
+  * Bugfix: If the UUID of a remote is not known, prevent --from, --to,
+    and other ways of specifying remotes by name from selecting it,
+    since it is not possible to sanely use it.
 
  -- Joey Hess <joeyh@debian.org>  Wed, 27 Feb 2013 23:20:40 -0400