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|
{- git-union-merge library
-
- Copyright 2011 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Git.UnionMerge (
merge,
mergeIndex
) where
import qualified Data.ByteString.Lazy as L
import qualified Data.Set as S
import Common
import Git
import Git.Sha
import Git.CatFile
import Git.Command
import Git.UpdateIndex
import Git.HashObject
import Git.Types
import Git.FilePath
{- 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
hashhandle <- hashObjectStart repo
ch <- catFileStart repo
streamUpdateIndex repo
[ lsTree x repo
, mergeTrees x y hashhandle ch repo
]
catFileStop ch
hashObjectStop hashhandle
{- Merges a list of branches into the index. Previously staged changes in
- the index are preserved (and participate in the merge).
-
- update-index is run once per ref in turn, so that each ref is merged on
- top of the merge for the previous ref. It would be more efficient, but
- harder to calculate a single union merge involving all the refs, as well
- as the index.
-}
mergeIndex :: HashObjectHandle -> CatFileHandle -> Repo -> [Ref] -> IO ()
mergeIndex hashhandle ch repo bs = forM_ bs $ \b ->
streamUpdateIndex repo [mergeTreeIndex b hashhandle ch repo]
{- For merging two trees. -}
mergeTrees :: Ref -> Ref -> HashObjectHandle -> CatFileHandle -> Repo -> Streamer
mergeTrees (Ref x) (Ref y) hashhandle ch = doMerge hashhandle ch
("diff-tree":diffOpts ++ [x, y, "--"])
{- For merging a single tree into the index. -}
mergeTreeIndex :: Ref -> HashObjectHandle -> CatFileHandle -> Repo -> Streamer
mergeTreeIndex (Ref r) hashhandle ch = doMerge hashhandle ch $
"diff-index" : diffOpts ++ ["--cached", r, "--"]
diffOpts :: [String]
diffOpts = ["--raw", "-z", "-r", "--no-renames", "-l0"]
{- Streams update-index changes to perform a merge,
- using git to get a raw diff. -}
doMerge :: HashObjectHandle -> CatFileHandle -> [String] -> Repo -> Streamer
doMerge hashhandle ch differ repo streamer = do
(diff, cleanup) <- pipeNullSplit (map Param differ) repo
go diff
void $ cleanup
where
go [] = noop
go (info:file:rest) = mergeFile info file hashhandle ch >>=
maybe (go rest) (\l -> streamer l >> go rest)
go (_:[]) = error $ "parse error " ++ show differ
{- 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 -> HashObjectHandle -> CatFileHandle -> IO (Maybe String)
mergeFile info file hashhandle h = case filter (/= nullSha) [Ref asha, Ref bsha] of
[] -> return Nothing
(sha:[]) -> use sha
shas -> use
=<< either return (\s -> hashBlob hashhandle (unlines s))
=<< calcMerge . zip shas <$> mapM getcontents shas
where
[_colonmode, _bmode, asha, bsha, _status] = words info
use sha = return $ Just $
updateIndexLine sha FileBlob $ asTopFilePath file
-- We don't know how the file is encoded, but need to
-- split it into lines to union merge. Using the
-- FileSystemEncoding for this is a hack, but ensures there
-- are no decoding errors. Note that this works because
-- hashObject sets fileEncoding on its write handle.
getcontents s = lines . encodeW8NUL . L.unpack <$> catObject h s
{- 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
|
