git-annex/Annex/TaggedPush.hs

{- git-annex tagged pushes
 -
 - Copyright 2012 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU AGPL version 3 or higher.
 -}

{-# LANGUAGE OverloadedStrings #-}

module Annex.TaggedPush where

import Annex.Common
import qualified Remote
import qualified Annex.Branch
import qualified Git
import qualified Git.Ref
import qualified Git.Command
import qualified Git.Branch
import Utility.Base64

import qualified Data.ByteString as S

{- Converts a git branch into a branch that is tagged with a UUID, typically
 - the UUID of the repo that will be pushing it, and possibly with other
 - information.
 -
 - Pushing to branches on the remote that have our uuid in them is ugly,
 - but it reserves those branches for pushing by us, and so our pushes will
 - never conflict with other pushes.
 -
 - To avoid cluttering up the branch display, the branch is put under
 - refs/synced/, rather than the usual refs/remotes/
 -
 - Both UUIDs and Base64 encoded data are always legal to be used in git
 - refs, per git-check-ref-format.
 -}
toTaggedBranch :: UUID -> Maybe String -> Git.Branch -> Git.Ref
toTaggedBranch u info b = Git.Ref $ S.intercalate "/" $ catMaybes
	[ Just "refs/synced"
	, Just $ fromUUID u
	, toB64' . encodeBS <$> info
	, Just $ Git.fromRef' $ Git.Ref.base b
	]

fromTaggedBranch :: Git.Ref -> Maybe (UUID, Maybe String)
fromTaggedBranch b = case splitc '/' $ Git.fromRef b of
	("refs":"synced":u:info:_base) ->
		Just (toUUID u, fromB64Maybe info)
	("refs":"synced":u:_base) ->
		Just (toUUID u, Nothing)
	_ -> Nothing

listTaggedBranches :: Annex [(Git.Sha, Git.Ref)]
listTaggedBranches = filter (isJust . fromTaggedBranch . snd)
	<$> inRepo Git.Ref.list

taggedPush :: UUID -> Maybe String -> Git.Ref -> Remote -> Git.Repo -> IO Bool
taggedPush u info branch remote = Git.Command.runBool
	[ Param "push"
	, Param $ Remote.name remote
	{- Using forcePush here is safe because we "own" the tagged branch
	 - we're pushing; it has no other writers. Ensures it is pushed
	 - even if it has been rewritten by a transition. -}
	, Param $ Git.Branch.forcePush $ refspec Annex.Branch.name
	, Param $ refspec branch
	]
  where
	refspec b = Git.fromRef b ++ ":" ++ Git.fromRef (toTaggedBranch u info b)