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|
{- git-union-merge library
-
- Copyright 2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Git.UnionMerge (
merge,
merge_index
) where
import System.Cmd.Utils
import qualified Data.Text.Lazy as L
import qualified Data.Text.Lazy.Encoding as L
import qualified Data.Set as S
import Common
import Git
import Git.Sha
import Git.CatFile
import Git.Command
import Git.UpdateIndex
{- Performs a union merge between two branches, staging it in the index.
- Any previously staged changes in the index will be lost.
-
- Should be run with a temporary index file configured by useIndex.
-}
merge :: Ref -> Ref -> Repo -> IO ()
merge x y repo = do
h <- catFileStart repo
stream_update_index repo
[ ls_tree x repo
, merge_trees x y h repo
]
catFileStop h
{- Merges a list of branches into the index. Previously staged changed in
- the index are preserved (and participate in the merge). -}
merge_index :: CatFileHandle -> Repo -> [Ref] -> IO ()
merge_index h repo bs =
stream_update_index repo $ map (\b -> merge_tree_index b h repo) bs
{- For merging two trees. -}
merge_trees :: Ref -> Ref -> CatFileHandle -> Repo -> Streamer
merge_trees (Ref x) (Ref y) h = calc_merge h $ "diff-tree":diff_opts ++ [x, y]
{- For merging a single tree into the index. -}
merge_tree_index :: Ref -> CatFileHandle -> Repo -> Streamer
merge_tree_index (Ref x) h = calc_merge h $
"diff-index" : diff_opts ++ ["--cached", x]
diff_opts :: [String]
diff_opts = ["--raw", "-z", "-r", "--no-renames", "-l0"]
{- Calculates how to perform a merge, using git to get a raw diff,
- and generating update-index input. -}
calc_merge :: CatFileHandle -> [String] -> Repo -> Streamer
calc_merge ch differ repo streamer = gendiff >>= go
where
gendiff = pipeNullSplit (map Param differ) repo
go [] = noop
go (info:file:rest) = mergeFile info file ch repo >>=
maybe (go rest) (\l -> streamer l >> go rest)
go (_:[]) = error "calc_merge parse error"
{- Given an info line from a git raw diff, and the filename, generates
- a line suitable for update-index that union merges the two sides of the
- diff. -}
mergeFile :: String -> FilePath -> CatFileHandle -> Repo -> IO (Maybe String)
mergeFile info file h repo = case filter (/= nullSha) [Ref asha, Ref bsha] of
[] -> return Nothing
(sha:[]) -> use sha
shas -> use =<< either return (hashObject repo . unlines) =<<
calcMerge . zip shas <$> mapM getcontents shas
where
[_colonmode, _bmode, asha, bsha, _status] = words info
getcontents s = map L.unpack . L.lines .
L.decodeUtf8 <$> catObject h s
use sha = return $ Just $ update_index_line sha file
{- Injects some content into git, returning its Sha. -}
hashObject :: Repo -> String -> IO Sha
hashObject repo content = getSha subcmd $ do
(h, s) <- pipeWriteRead (map Param params) content repo
length s `seq` do
forceSuccess h
reap -- XXX unsure why this is needed
return s
where
subcmd = "hash-object"
params = [subcmd, "-w", "--stdin"]
{- Calculates a union merge between a list of refs, with contents.
-
- When possible, reuses the content of an existing ref, rather than
- generating new content.
-}
calcMerge :: [(Ref, [String])] -> Either Ref [String]
calcMerge shacontents
| null reuseable = Right $ new
| otherwise = Left $ fst $ Prelude.head reuseable
where
reuseable = filter (\c -> sorteduniq (snd c) == new) shacontents
new = sorteduniq $ concat $ map snd shacontents
sorteduniq = S.toList . S.fromList
|
