110 lines
3.6 KiB
Haskell
110 lines
3.6 KiB
Haskell
{- git-union-merge library
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-
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- Copyright 2011 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Git.UnionMerge (
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merge,
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mergeIndex
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) where
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import qualified Data.ByteString.Lazy as L
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import qualified Data.Set as S
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import Common
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import Git
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import Git.Sha
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import Git.CatFile
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import Git.Command
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import Git.UpdateIndex
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import Git.HashObject
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import Git.Types
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import Git.FilePath
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{- Performs a union merge between two branches, staging it in the index.
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- Any previously staged changes in the index will be lost.
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-
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- Should be run with a temporary index file configured by useIndex.
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-}
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merge :: Ref -> Ref -> Repo -> IO ()
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merge x y repo = do
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h <- catFileStart repo
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streamUpdateIndex repo
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[ lsTree x repo
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, mergeTrees x y h repo
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]
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catFileStop h
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{- Merges a list of branches into the index. Previously staged changes in
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- the index are preserved (and participate in the merge).
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-
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- update-index is run once per ref in turn, so that each ref is merged on
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- top of the merge for the previous ref. It would be more efficient, but
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- harder to calculate a single union merge involving all the refs, as well
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- as the index.
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-}
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mergeIndex :: CatFileHandle -> Repo -> [Ref] -> IO ()
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mergeIndex h repo bs = forM_ bs $ \b ->
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streamUpdateIndex repo [mergeTreeIndex b h repo]
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{- For merging two trees. -}
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mergeTrees :: Ref -> Ref -> CatFileHandle -> Repo -> Streamer
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mergeTrees (Ref x) (Ref y) h = doMerge h $ "diff-tree":diffOpts ++ [x, y]
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{- For merging a single tree into the index. -}
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mergeTreeIndex :: Ref -> CatFileHandle -> Repo -> Streamer
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mergeTreeIndex (Ref x) h = doMerge h $
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"diff-index" : diffOpts ++ ["--cached", x]
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diffOpts :: [String]
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diffOpts = ["--raw", "-z", "-r", "--no-renames", "-l0"]
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{- Streams update-index changes to perform a merge,
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- using git to get a raw diff. -}
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doMerge :: CatFileHandle -> [String] -> Repo -> Streamer
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doMerge ch differ repo streamer = do
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(diff, cleanup) <- pipeNullSplit (map Param differ) repo
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go diff
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void $ cleanup
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where
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go [] = noop
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go (info:file:rest) = mergeFile info file ch repo >>=
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maybe (go rest) (\l -> streamer l >> go rest)
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go (_:[]) = error $ "parse error " ++ show differ
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{- Given an info line from a git raw diff, and the filename, generates
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- a line suitable for update-index that union merges the two sides of the
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- diff. -}
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mergeFile :: String -> FilePath -> CatFileHandle -> Repo -> IO (Maybe String)
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mergeFile info file h repo = case filter (/= nullSha) [Ref asha, Ref bsha] of
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[] -> return Nothing
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(sha:[]) -> use sha
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shas -> use
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=<< either return (\s -> hashObject BlobObject (unlines s) repo)
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=<< calcMerge . zip shas <$> mapM getcontents shas
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where
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[_colonmode, _bmode, asha, bsha, _status] = words info
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use sha = return $ Just $
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updateIndexLine sha FileBlob $ asTopFilePath file
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-- We don't know how the file is encoded, but need to
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-- split it into lines to union merge. Using the
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-- FileSystemEncoding for this is a hack, but ensures there
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-- are no decoding errors. Note that this works because
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-- hashObject sets fileEncoding on its write handle.
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getcontents s = lines . encodeW8 . L.unpack <$> catObject h s
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{- Calculates a union merge between a list of refs, with contents.
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-
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- When possible, reuses the content of an existing ref, rather than
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- generating new content.
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-}
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calcMerge :: [(Ref, [String])] -> Either Ref [String]
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calcMerge shacontents
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| null reuseable = Right $ new
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| otherwise = Left $ fst $ Prelude.head reuseable
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where
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reuseable = filter (\c -> sorteduniq (snd c) == new) shacontents
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new = sorteduniq $ concat $ map snd shacontents
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sorteduniq = S.toList . S.fromList
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