109 lines
3.6 KiB
Haskell
109 lines
3.6 KiB
Haskell
{- git-union-merge library
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-
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- Copyright 2011 Joey Hess <joey@kitenet.net>
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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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update_index,
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update_index_line,
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ls_tree
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) where
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import System.Cmd.Utils
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import Data.List
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import Data.Maybe
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import Data.String.Utils
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import qualified Data.ByteString.Lazy.Char8 as L
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import Git
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import qualified Git.ByteString as GitB
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import Utility.SafeCommand
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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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- When only one branch is specified, it is merged into the index.
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- In this case, previously staged changes in the index are preserved.
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-
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- Should be run with a temporary index file configured by Git.useIndex.
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-}
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merge :: Repo -> [String] -> IO ()
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merge g (x:y:[]) = do
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a <- ls_tree g x
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b <- merge_trees g x y
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update_index g (a++b)
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merge g [x] = merge_tree_index g x >>= update_index g
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merge _ _ = error "wrong number of branches to merge"
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{- Feeds a list into update-index. Later items in the list can override
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- earlier ones, so the list can be generated from any combination of
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- ls_tree, merge_trees, and merge_tree_index. -}
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update_index :: Repo -> [String] -> IO ()
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update_index g l = togit ["update-index", "-z", "--index-info"] (join "\0" l)
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where
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togit ps content = pipeWrite g (map Param ps) content
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>>= forceSuccess
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{- Generates a line suitable to be fed into update-index, to add
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- a given file with a given sha. -}
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update_index_line :: String -> FilePath -> String
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update_index_line sha file = "100644 blob " ++ sha ++ "\t" ++ file
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{- Gets the contents of a tree in a format suitable for update_index. -}
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ls_tree :: Repo -> String -> IO [String]
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ls_tree g x = pipeNullSplit g $
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map Param ["ls-tree", "-z", "-r", "--full-tree", x]
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{- For merging two trees. -}
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merge_trees :: Repo -> String -> String -> IO [String]
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merge_trees g x y = calc_merge g $ "diff-tree":diff_opts ++ [x, y]
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{- For merging a single tree into the index. -}
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merge_tree_index :: Repo -> String -> IO [String]
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merge_tree_index g x = calc_merge g $ "diff-index":diff_opts ++ ["--cached", x]
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diff_opts :: [String]
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diff_opts = ["--raw", "-z", "-r", "--no-renames", "-l0"]
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{- Calculates how to perform a merge, using git to get a raw diff,
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- and returning a list suitable for update_index. -}
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calc_merge :: Repo -> [String] -> IO [String]
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calc_merge g differ = do
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diff <- pipeNullSplit g $ map Param differ
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l <- mapM (mergeFile g) (pairs diff)
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return $ catMaybes l
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where
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pairs [] = []
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pairs (_:[]) = error "calc_merge parse error"
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pairs (a:b:rest) = (a,b):pairs rest
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{- Injects some content into git, returning its hash. -}
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hashObject :: Repo -> L.ByteString -> IO String
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hashObject repo content = getSha subcmd $ do
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(h, s) <- GitB.pipeWriteRead repo (map Param params) content
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L.length s `seq` do
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forceSuccess h
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reap -- XXX unsure why this is needed
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return $ L.unpack s
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where
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subcmd = "hash-object"
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params = [subcmd, "-w", "--stdin"]
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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 :: Repo -> (String, FilePath) -> IO (Maybe String)
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mergeFile g (info, file) = case filter (/= nullsha) [asha, bsha] of
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[] -> return Nothing
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(sha:[]) -> return $ Just $ update_index_line sha file
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shas -> do
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content <- GitB.pipeRead g $ map Param ("show":shas)
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sha <- hashObject g $ unionmerge content
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return $ Just $ update_index_line sha file
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where
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[_colonamode, _bmode, asha, bsha, _status] = words info
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nullsha = replicate shaSize '0'
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unionmerge = L.unlines . nub . L.lines
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