add git ls-tree --long parser

Not yet used, but allows getting the size of items in the tree fairly
cheaply.

I noticed that CmdLine.Seek uses ls-tree and the feeds the files into
another long-running process to check their size. That would be an
example of a place that might be sped up by using this. Although in that
particular case, it only needs to know the size of unlocked files, not
locked. And since enabling --long probably doubles the ls-tree runtime
or more, the overhead of using it there may outwweigh the benefit.

Logs/Export.hs

@@ -204,5 +204,5 @@ getExportExcluded u = do
 exportExcludedParser :: L.ByteString -> [Git.Tree.TreeItem]
 exportExcludedParser = map Git.Tree.lsTreeItemToTreeItem
 	. rights
-	. map Git.LsTree.parseLsTree
+	. map (Git.LsTree.parseLsTree (Git.LsTree.LsTreeLong False))
 	. L.split (fromIntegral $ ord '\n')

Logs/Web.hs

@@ -97,6 +97,7 @@ withKnownUrls a = do
 	Annex.Branch.commit =<< Annex.Branch.commitMessage
 	(l, cleanup) <- inRepo $ Git.LsTree.lsTree
 		Git.LsTree.LsTreeRecursive
+		(Git.LsTree.LsTreeLong False)
 		Annex.Branch.fullname
 	g <- Annex.gitRepo
 	let want = urlLogFileKey . getTopFilePath . Git.LsTree.file