git-annex/Annex/CatFile.hs

{- git cat-file interface, with handle automatically stored in the Annex monad
 -
 - Copyright 2011 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Annex.CatFile (
	catFile,
	catObject,
	catObjectDetails,
	catFileHandle,
	catKey,
	catKeyFile,
) where

import qualified Data.ByteString.Lazy as L

import Common.Annex
import qualified Git
import qualified Git.CatFile
import qualified Annex
import Git.Types

catFile :: Git.Branch -> FilePath -> Annex L.ByteString
catFile branch file = do
	h <- catFileHandle
	liftIO $ Git.CatFile.catFile h branch file

catObject :: Git.Ref -> Annex L.ByteString
catObject ref = do
	h <- catFileHandle
	liftIO $ Git.CatFile.catObject h ref

catObjectDetails :: Git.Ref -> Annex (Maybe (L.ByteString, Sha))
catObjectDetails ref = do
	h <- catFileHandle
	liftIO $ Git.CatFile.catObjectDetails h ref

catFileHandle :: Annex Git.CatFile.CatFileHandle
catFileHandle = maybe startup return =<< Annex.getState Annex.catfilehandle
  where
	startup = do
		h <- inRepo Git.CatFile.catFileStart
		Annex.changeState $ \s -> s { Annex.catfilehandle = Just h }
		return h

{- From the Sha or Ref of a symlink back to the key. -}
catKey :: Ref -> Annex (Maybe Key)
catKey ref = do
	l <- encodeW8 . L.unpack  <$> catObject ref
	return $ if isLinkToAnnex l
		then fileKey $ takeFileName l
		else Nothing

{- From a file in git back to the key.
 -
 - Prefixing the file with ./ makes this work even if in a subdirectory
 - of a repo. For some reason, HEAD is sometimes needed.
 -}
catKeyFile :: FilePath -> Annex (Maybe Key)
catKeyFile f = catKey $ Ref $ "HEAD:./" ++ f