--inbackend can be used to make git-annex only operate on files whose content is stored using a specified key-value backend.

GitAnnex.hs

@@ -111,6 +111,8 @@ options = commonOptions ++
 		"skip files not present in a remote"
 	, Option ['C'] ["copies"] (ReqArg Limit.addCopies paramNumber)
 		"skip files with fewer copies"
+	, Option ['B'] ["inbackend"] (ReqArg Limit.addInBackend paramName)
+		"skip files not using a key-value backend"
 	] ++ matcherOptions
 	where
 		setto v = Annex.changeState $ \s -> s { Annex.toremote = Just v }

Limit.hs

@@ -88,3 +88,10 @@ addCopies num =
 		handle n (Just (key, _)) = do
 			us <- keyLocations key
 			return $ length us >= n
+
+{- Adds a limit to skip files not using a specified key-value backend. -}
+addInBackend :: String -> Annex ()
+addInBackend name = addLimit $ Backend.lookupFile >=> check
+	where
+		wanted = Backend.lookupBackendName name
+		check = return . maybe False ((==) wanted . snd)

debian/changelog

@@ -8,6 +8,8 @@ git-annex (3.20111123) UNRELEASED; urgency=low
   * Bugfix: dropunused did not drop keys with two spaces in their name.
   * Support for storing .git/annex on a different device than the rest of the
     git repository.
+  * --inbackend can be used to make git-annex only operate on files
+    whose content is stored using a specified key-value backend.
 
  -- Joey Hess <joeyh@debian.org>  Tue, 22 Nov 2011 17:53:42 -0400
 

doc/git-annex.mdwn

@@ -446,6 +446,11 @@ file contents are present at either of two repositories.
   Matches only files that git-annex believes to have the specified number
   of copies, or more.
 
+* --inbackend=name
+
+  Matches only files whose content is stored using the specified key-value
+  backend.
+
 * --not
 
   Inverts the next file matching option. For example, to only act on