rename GitUnionMerge to Git.UnionMerge

Also, moved commit function into Git proper, it's not union merge specific.

Git/UnionMerge.hs

@@ -0,0 +1,95 @@
+{- git-union-merge library
+ -
+ - Copyright 2011 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Git.UnionMerge (
+	merge,
+	update_index,
+	update_index_line,
+	ls_tree
+) where
+
+import System.Cmd.Utils
+import Data.List
+import Data.Maybe
+import Data.String.Utils
+
+import Git
+import Utility
+
+{- Performs a union merge between two branches, staging it in the index.
+ - Any previously staged changes in the index will be lost.
+ -
+ - When only one branch is specified, it is merged into the index.
+ - In this case, previously staged changes in the index are preserved.
+ -
+ - Should be run with a temporary index file configured by Git.useIndex.
+ -}
+merge :: Repo -> [String] -> IO ()
+merge g (x:y:[]) = do
+	a <- ls_tree g x
+	b <- merge_trees g x y
+	update_index g (a++b)
+merge g [x] = merge_tree_index g x >>= update_index g
+merge _ _ = error "wrong number of branches to merge"
+
+{- Feeds a list into update-index. Later items in the list can override
+ - earlier ones, so the list can be generated from any combination of
+ - ls_tree, merge_trees, and merge_tree_index. -}
+update_index :: Repo -> [String] -> IO ()
+update_index g l = togit ["update-index", "-z", "--index-info"] (join "\0" l)
+	where
+		togit ps content = pipeWrite g (map Param ps) content
+			>>= forceSuccess
+
+{- Generates a line suitable to be fed into update-index, to add
+ - a given file with a given sha. -}
+update_index_line :: String -> FilePath -> String
+update_index_line sha file = "100644 blob " ++ sha ++ "\t" ++ file
+
+{- Gets the contents of a tree in a format suitable for update_index. -}
+ls_tree :: Repo -> String -> IO [String]
+ls_tree g x = pipeNullSplit g $ 
+	map Param ["ls-tree", "-z", "-r", "--full-tree", x]
+
+{- For merging two trees. -}
+merge_trees :: Repo -> String -> String -> IO [String]
+merge_trees g x y = calc_merge g $ "diff-tree":diff_opts ++ [x, y]
+
+{- For merging a single tree into the index. -}
+merge_tree_index :: Repo -> String -> IO [String]
+merge_tree_index g x = calc_merge g $ "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 returning a list suitable for update_index. -}
+calc_merge :: Repo -> [String] -> IO [String]
+calc_merge g differ = do
+	diff <- pipeNullSplit g $ map Param differ
+	l <- mapM (mergeFile g) (pairs diff)
+	return $ catMaybes l
+	where
+		pairs [] = []
+		pairs (_:[]) = error "calc_merge parse error"
+		pairs (a:b:rest) = (a,b):pairs rest
+
+{- 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 :: Repo -> (String, FilePath) -> IO (Maybe String)
+mergeFile g (info, file) = case filter (/= nullsha) [asha, bsha] of
+	[] -> return Nothing
+	(sha:[]) -> return $ Just $ update_index_line sha file
+	shas -> do
+		content <- pipeRead g $ map Param ("show":shas)
+		sha <- hashObject g $ unionmerge content
+		return $ Just $ update_index_line sha file
+	where
+		[_colonamode, _bmode, asha, bsha, _status] = words info
+		nullsha = take shaSize $ repeat '0'
+		unionmerge = unlines . nub . lines