git-annex/Git/Command.hs

{- running git commands
 -
 - Copyright 2010-2012 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Git.Command where

import System.Posix.Process (getAnyProcessStatus)

import Common
import Git
import Git.Types

{- Constructs a git command line operating on the specified repo. -}
gitCommandLine :: [CommandParam] -> Repo -> [CommandParam]
gitCommandLine params Repo { location = l@(Local _ _ ) } = setdir : settree ++ params
	where
		setdir = Param $ "--git-dir=" ++ gitdir l
		settree = case worktree l of
			Nothing -> []
			Just t -> [Param $ "--work-tree=" ++ t]
gitCommandLine _ repo = assertLocal repo $ error "internal"

{- Runs git in the specified repo. -}
runBool :: String -> [CommandParam] -> Repo -> IO Bool
runBool subcommand params repo = assertLocal repo $
	boolSystem "git" $ gitCommandLine (Param subcommand : params) repo

{- Runs git in the specified repo, throwing an error if it fails. -}
run :: String -> [CommandParam] -> Repo -> IO ()
run subcommand params repo = assertLocal repo $
	unlessM (runBool subcommand params repo) $
		error $ "git " ++ subcommand ++ " " ++ show params ++ " failed"

{- Runs a git subcommand and returns its output, lazily. 
 -
 - Note that this leaves the git process running, and so zombies will
 - result unless reap is called.
 -}
pipeRead :: [CommandParam] -> Repo -> IO String
pipeRead params repo = assertLocal repo $
	withHandle StdoutHandle createBackgroundProcess p $ \h -> do
		fileEncoding h
		hGetContents h
	where
		p  = proc "git" $ toCommand $ gitCommandLine params repo

{- Runs a git subcommand, feeding it input, and returning its output,
 - which is expected to be fairly small, since it's all read into memory
 - strictly. -}
pipeWriteRead :: [CommandParam] -> String -> Repo -> IO String
pipeWriteRead params s repo = assertLocal repo $
	writeReadProcess "git" (toCommand $ gitCommandLine params repo) s

{- Reads null terminated output of a git command (as enabled by the -z 
 - parameter), and splits it. -}
pipeNullSplit :: [CommandParam] -> Repo -> IO [String]
pipeNullSplit params repo =
	filter (not . null) . split sep <$> pipeRead params repo
	where
		sep = "\0"

{- Reaps any zombie git processes. -}
reap :: IO ()
reap = do
	-- throws an exception when there are no child processes
	catchDefaultIO (getAnyProcessStatus False True) Nothing
		>>= maybe noop (const reap)