Revert "disable filter.annex.process in restagePointerFile"

This reverts commit afe327ac49.

Unfortunately, disabling it by setting it to "" does not work, git
then ignores filter.annex.smudge/clean, and does not pass files through
git-annex at all.

I don't think there is a way to temporarily disable this git config
from the git command line. Which seems like a bug in git.

So, it may be more expensive than anticipated to enable
filter.annex.process, since git checkout etc will pipe all annexed files
being checked out through it.

Annex/Link.hs

@@ -221,18 +221,10 @@ restagePointerFile (Restage True) f orig = withTSDelta $ \tsd ->
 			let updatetmpindex = do
 				r' <- liftIO $ Git.Env.addGitEnv r Git.Index.indexEnv
 					=<< Git.Index.indexEnvVal (toRawFilePath tmpindex)
-				let r'' = r' { gitGlobalOpts = gitGlobalOpts r' ++
 				-- Avoid git warning about CRLF munging.
+				let r'' = r' { gitGlobalOpts = gitGlobalOpts r' ++
 					[ Param "-c"
 					, Param $ "core.safecrlf=" ++ boolConfig False
-					-- Avoid using git-annex
-					-- filter-process, because git
-					-- pipes the content of annexed
-					-- files into it; using
-					-- git-annex smudge --clean is
-					-- probably faster.
-					, Param "-c"
-					, Param $ "filter.annex.process="
 					] }
 				runsGitAnnexChildProcessViaGit' r'' $ \r''' ->
 					liftIO $ Git.UpdateIndex.refreshIndex r''' $ \feed ->