git-annex/Git/CatFile.hs
Joey Hess ea3cb7d277
fix a case where file tracked by git unexpectedly becomes annex pointer file
smudge: When annex.largefiles=anything, files that were already stored in
git, and have not been modified could sometimes be converted to being
stored in the annex. Changes in 7.20191024 made this more of a problem.
This case is now detected and prevented.
2019-12-27 15:08:03 -04:00

259 lines
8.3 KiB
Haskell

{- git cat-file interface
-
- Copyright 2011-2019 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
module Git.CatFile (
CatFileHandle,
catFileStart,
catFileStart',
catFileStop,
catFile,
catFileDetails,
catTree,
catCommit,
catObject,
catObjectDetails,
catObjectMetaData,
) where
import System.IO
import qualified Data.ByteString as S
import qualified Data.ByteString.Lazy as L
import qualified Data.ByteString.Lazy.Char8 as L8
import qualified Data.Map as M
import Data.String
import Data.Char
import Numeric
import System.Posix.Types
import Text.Read
import Common
import Git
import Git.Sha
import qualified Git.Ref
import Git.Command
import Git.Types
import Git.FilePath
import Git.HashObject
import qualified Utility.CoProcess as CoProcess
import Utility.Tuple
data CatFileHandle = CatFileHandle
{ catFileProcess :: CoProcess.CoProcessHandle
, checkFileProcess :: CoProcess.CoProcessHandle
, gitRepo :: Repo
}
catFileStart :: Repo -> IO CatFileHandle
catFileStart = catFileStart' True
catFileStart' :: Bool -> Repo -> IO CatFileHandle
catFileStart' restartable repo = CatFileHandle
<$> startp "--batch"
<*> startp "--batch-check=%(objectname) %(objecttype) %(objectsize)"
<*> pure repo
where
startp p = gitCoProcessStart restartable
[ Param "cat-file"
, Param p
] repo
catFileStop :: CatFileHandle -> IO ()
catFileStop h = do
CoProcess.stop (catFileProcess h)
CoProcess.stop (checkFileProcess h)
{- Reads a file from a specified branch. -}
catFile :: CatFileHandle -> Branch -> RawFilePath -> IO L.ByteString
catFile h branch file = catObject h $ Ref $
fromRef branch ++ ":" ++ fromRawFilePath (toInternalGitPath file)
catFileDetails :: CatFileHandle -> Branch -> RawFilePath -> IO (Maybe (L.ByteString, Sha, ObjectType))
catFileDetails h branch file = catObjectDetails h $ Ref $
fromRef branch ++ ":" ++ fromRawFilePath (toInternalGitPath file)
{- Uses a running git cat-file read the content of an object.
- Objects that do not exist will have "" returned. -}
catObject :: CatFileHandle -> Ref -> IO L.ByteString
catObject h object = maybe L.empty fst3 <$> catObjectDetails h object
catObjectDetails :: CatFileHandle -> Ref -> IO (Maybe (L.ByteString, Sha, ObjectType))
catObjectDetails h object = query (catFileProcess h) object newlinefallback $ \from -> do
header <- hGetLine from
case parseResp object header of
Just (ParsedResp sha size objtype) -> do
content <- S.hGet from (fromIntegral size)
eatchar '\n' from
return $ Just (L.fromChunks [content], sha, objtype)
Just DNE -> return Nothing
Nothing -> error $ "unknown response from git cat-file " ++ show (header, object)
where
eatchar expected from = do
c <- hGetChar from
when (c /= expected) $
error $ "missing " ++ (show expected) ++ " from git cat-file"
-- Slow fallback path for filenames containing newlines.
newlinefallback = queryObjectType object (gitRepo h) >>= \case
Nothing -> return Nothing
Just objtype -> queryContent object (gitRepo h) >>= \case
Nothing -> return Nothing
Just content -> do
-- only the --batch interface allows getting
-- the sha, so have to re-hash the object
sha <- hashObject' objtype
(flip L.hPut content)
(gitRepo h)
return (Just (content, sha, objtype))
{- Gets the size and type of an object, without reading its content. -}
catObjectMetaData :: CatFileHandle -> Ref -> IO (Maybe (Sha, FileSize, ObjectType))
catObjectMetaData h object = query (checkFileProcess h) object newlinefallback $ \from -> do
resp <- hGetLine from
case parseResp object resp of
Just (ParsedResp sha size objtype) ->
return $ Just (sha, size, objtype)
Just DNE -> return Nothing
Nothing -> error $ "unknown response from git cat-file " ++ show (resp, object)
where
-- Slow fallback path for filenames containing newlines.
newlinefallback = do
sha <- Git.Ref.sha object (gitRepo h)
sz <- querySize object (gitRepo h)
objtype <- queryObjectType object (gitRepo h)
return $ (,,) <$> sha <*> sz <*> objtype
data ParsedResp = ParsedResp Sha FileSize ObjectType | DNE
query :: CoProcess.CoProcessHandle -> Ref -> IO a -> (Handle -> IO a) -> IO a
query hdl object newlinefallback receive
-- git cat-file --batch uses a line based protocol, so when the
-- filename itself contains a newline, have to fall back to another
-- method of getting the information.
| '\n' `elem` s = newlinefallback
-- git strips carriage return from the end of a line, out of some
-- misplaced desire to support windows, so also use the newline
-- fallback for those.
| "\r" `isSuffixOf` s = newlinefallback
| otherwise = CoProcess.query hdl send receive
where
send to = hPutStrLn to s
s = fromRef object
parseResp :: Ref -> String -> Maybe ParsedResp
parseResp object l
| " missing" `isSuffixOf` l -- less expensive than full check
&& l == fromRef object ++ " missing" = Just DNE
| otherwise = case words l of
[sha, objtype, size]
| length sha == shaSize ->
case (readObjectType (encodeBS objtype), reads size) of
(Just t, [(bytes, "")]) ->
Just $ ParsedResp (Ref sha) bytes t
_ -> Nothing
| otherwise -> Nothing
_ -> Nothing
querySingle :: CommandParam -> Ref -> Repo -> (Handle -> IO a) -> IO (Maybe a)
querySingle o r repo reader = assertLocal repo $
-- In non-batch mode, git cat-file warns on stderr when
-- asked for an object that does not exist.
-- Squelch that warning to behave the same as batch mode.
withNullHandle $ \nullh -> do
let p = gitCreateProcess
[ Param "cat-file"
, o
, Param (fromRef r)
] repo
let p' = p
{ std_err = UseHandle nullh
, std_in = Inherit
, std_out = CreatePipe
}
pid <- createProcess p'
let h = stdoutHandle pid
output <- reader h
hClose h
ifM (checkSuccessProcess (processHandle pid))
( return (Just output)
, return Nothing
)
querySize :: Ref -> Repo -> IO (Maybe FileSize)
querySize r repo = maybe Nothing (readMaybe . takeWhile (/= '\n'))
<$> querySingle (Param "-s") r repo hGetContentsStrict
queryObjectType :: Ref -> Repo -> IO (Maybe ObjectType)
queryObjectType r repo = maybe Nothing (readObjectType . encodeBS . takeWhile (/= '\n'))
<$> querySingle (Param "-t") r repo hGetContentsStrict
queryContent :: Ref -> Repo -> IO (Maybe L.ByteString)
queryContent r repo = fmap (\b -> L.fromChunks [b])
<$> querySingle (Param "-p") r repo S.hGetContents
{- Gets a list of files and directories in a tree. (Not recursive.) -}
catTree :: CatFileHandle -> Ref -> IO [(FilePath, FileMode)]
catTree h treeref = go <$> catObjectDetails h treeref
where
go (Just (b, _, TreeObject)) = parsetree [] b
go _ = []
parsetree c b = case L.break (== 0) b of
(modefile, rest)
| L.null modefile -> c
| otherwise -> parsetree
(parsemodefile modefile:c)
(dropsha rest)
-- these 20 bytes after the NUL hold the file's sha
dropsha = L.drop 21
parsemodefile b =
let (modestr, file) = separate (== ' ') (decodeBL b)
in (file, readmode modestr)
readmode = fromMaybe 0 . fmap fst . headMaybe . readOct
catCommit :: CatFileHandle -> Ref -> IO (Maybe Commit)
catCommit h commitref = go <$> catObjectDetails h commitref
where
go (Just (b, _, CommitObject)) = parseCommit b
go _ = Nothing
parseCommit :: L.ByteString -> Maybe Commit
parseCommit b = Commit
<$> (extractSha . L8.unpack =<< field "tree")
<*> Just (maybe [] (mapMaybe (extractSha . L8.unpack)) (fields "parent"))
<*> (parsemetadata <$> field "author")
<*> (parsemetadata <$> field "committer")
<*> Just (L8.unpack $ L.intercalate (L.singleton nl) message)
where
field n = headMaybe =<< fields n
fields n = M.lookup (fromString n) fieldmap
fieldmap = M.fromListWith (++) ((map breakfield) header)
breakfield l =
let (k, sp_v) = L.break (== sp) l
in (k, [L.drop 1 sp_v])
(header, message) = separate L.null ls
ls = L.split nl b
-- author and committer lines have the form: "name <email> date"
-- The email is always present, even if empty "<>"
parsemetadata l = CommitMetaData
{ commitName = whenset $ L.init name_sp
, commitEmail = whenset email
, commitDate = whenset $ L.drop 2 gt_sp_date
}
where
(name_sp, rest) = L.break (== lt) l
(email, gt_sp_date) = L.break (== gt) (L.drop 1 rest)
whenset v
| L.null v = Nothing
| otherwise = Just (L8.unpack v)
nl = fromIntegral (ord '\n')
sp = fromIntegral (ord ' ')
lt = fromIntegral (ord '<')
gt = fromIntegral (ord '>')