add new status command

This works for both direct and indirect mode.

It may need some performance tuning.

Note that unlike git status, it only shows the status of the work tree, not
the status of the index. So only one status letter, not two .. and since
files that have been added and not yet committed do not differ between the
work tree and the index, they are not shown. Might want to add display of
the index vs the last commit eventually.

This commit was sponsored by an unknown bitcoin contributor, whose
contribution as been going up lately! ;)

Annex/CatFile.hs

@@ -27,6 +27,7 @@ import qualified Annex
 import Git.Types
 import Git.FilePath
 import Git.FileMode
+import qualified Git.Ref
 
 catFile :: Git.Branch -> FilePath -> Annex L.ByteString
 catFile branch file = do
@@ -108,9 +109,6 @@ catKeyChecked needhead ref@(Ref r) =
 		 map snd . filter (\p -> fst p == file)
 
 {- From a file in the repository back to the key.
- -
- - Prefixing the file with ./ makes this work even if in a subdirectory
- - of a repo.
  -
  - Ideally, this should reflect the key that's staged in the index,
  - not the key that's committed to HEAD. Unfortunately, git cat-file
@@ -134,8 +132,8 @@ catKeyChecked needhead ref@(Ref r) =
 catKeyFile :: FilePath -> Annex (Maybe Key)
 catKeyFile f = ifM (Annex.getState Annex.daemon)
 	( catKeyFileHEAD f
-	, catKeyChecked True (Ref $ ":./" ++ f)
+	, catKeyChecked True $ Git.Ref.fileRef f
 	)
 
 catKeyFileHEAD :: FilePath -> Annex (Maybe Key)
-catKeyFileHEAD f = catKeyChecked False (Ref $ "HEAD:./" ++ f)
+catKeyFileHEAD f = catKeyChecked False $ Git.Ref.fileFromRef Git.Ref.headRef f