{- git-annex links to content - - On file systems that support them, symlinks are used. - - On other filesystems, git instead stores the symlink target in a regular - file. - - Pointer files are used instead of symlinks for unlocked files. - - Copyright 2013-2022 Joey Hess - - Licensed under the GNU AGPL version 3 or higher. -} {-# LANGUAGE CPP, BangPatterns, OverloadedStrings #-} module Annex.Link where import Annex.Common import qualified Annex import qualified Annex.Queue import qualified Git.Queue import qualified Git.UpdateIndex import qualified Git.Index import qualified Git.LockFile import qualified Git.Env import qualified Git import Logs.Restage import Git.Types import Git.FilePath import Git.Config import Annex.HashObject import Annex.InodeSentinal import Annex.PidLock import Utility.FileMode import Utility.InodeCache import Utility.Tmp.Dir import Utility.CopyFile import qualified Database.Keys.Handle import qualified Utility.RawFilePath as R import qualified Data.ByteString as S import qualified Data.ByteString.Char8 as S8 import qualified Data.ByteString.Lazy as L import qualified System.FilePath.ByteString as P #ifndef mingw32_HOST_OS import System.PosixCompat.Files (isSymbolicLink) #endif type LinkTarget = S.ByteString {- Checks if a file is a link to a key. -} isAnnexLink :: RawFilePath -> Annex (Maybe Key) isAnnexLink file = maybe Nothing parseLinkTargetOrPointer <$> getAnnexLinkTarget file {- Gets the link target of a symlink. - - On a filesystem that does not support symlinks, fall back to getting the - link target by looking inside the file. - - Returns Nothing if the file is not a symlink, or not a link to annex - content. -} getAnnexLinkTarget :: RawFilePath -> Annex (Maybe LinkTarget) getAnnexLinkTarget f = getAnnexLinkTarget' f =<< (coreSymlinks <$> Annex.getGitConfig) {- Pass False to force looking inside file, for when git checks out - symlinks as plain files. -} getAnnexLinkTarget' :: RawFilePath -> Bool -> Annex (Maybe S.ByteString) getAnnexLinkTarget' file coresymlinks = if coresymlinks then check probesymlink $ return Nothing else check probesymlink $ check probefilecontent $ return Nothing where check getlinktarget fallback = liftIO (catchMaybeIO getlinktarget) >>= \case Just l | isLinkToAnnex l -> return (Just l) | otherwise -> return Nothing Nothing -> fallback probesymlink = R.readSymbolicLink file probefilecontent = withFile (fromRawFilePath file) ReadMode $ \h -> do s <- S.hGet h maxSymlinkSz -- If we got the full amount, the file is too large -- to be a symlink target. return $ if S.length s == maxSymlinkSz then mempty else -- If there are any NUL or newline -- characters, or whitespace, we -- certainly don't have a symlink to a -- git-annex key. if any (`S8.elem` s) ("\0\n\r \t" :: [Char]) then mempty else s makeAnnexLink :: LinkTarget -> RawFilePath -> Annex () makeAnnexLink = makeGitLink {- Creates a link on disk. - - On a filesystem that does not support symlinks, writes the link target - to a file. Note that git will only treat the file as a symlink if - it's staged as such, so use addAnnexLink when adding a new file or - modified link to git. -} makeGitLink :: LinkTarget -> RawFilePath -> Annex () makeGitLink linktarget file = ifM (coreSymlinks <$> Annex.getGitConfig) ( liftIO $ do void $ tryIO $ R.removeLink file R.createSymbolicLink linktarget file , liftIO $ S.writeFile (fromRawFilePath file) linktarget ) {- Creates a link on disk, and additionally stages it in git. -} addAnnexLink :: LinkTarget -> RawFilePath -> Annex () addAnnexLink linktarget file = do makeAnnexLink linktarget file stageSymlink file =<< hashSymlink linktarget {- Injects a symlink target into git, returning its Sha. -} hashSymlink :: LinkTarget -> Annex Sha hashSymlink = hashBlob . toInternalGitPath {- Stages a symlink to an annexed object, using a Sha of its target. -} stageSymlink :: RawFilePath -> Sha -> Annex () stageSymlink file sha = Annex.Queue.addUpdateIndex =<< inRepo (Git.UpdateIndex.stageSymlink file sha) {- Injects a pointer file content into git, returning its Sha. -} hashPointerFile :: Key -> Annex Sha hashPointerFile key = hashBlob $ formatPointer key {- Stages a pointer file, using a Sha of its content -} stagePointerFile :: RawFilePath -> Maybe FileMode -> Sha -> Annex () stagePointerFile file mode sha = Annex.Queue.addUpdateIndex =<< inRepo (Git.UpdateIndex.stageFile sha treeitemtype file) where treeitemtype | maybe False isExecutable mode = TreeExecutable | otherwise = TreeFile writePointerFile :: RawFilePath -> Key -> Maybe FileMode -> IO () writePointerFile file k mode = do S.writeFile (fromRawFilePath file) (formatPointer k) maybe noop (R.setFileMode file) mode newtype Restage = Restage Bool {- Restage pointer file. This is used after updating a worktree file - when content is added/removed, to prevent git status from showing - it as modified. - - The InodeCache is for the worktree file. It is used to detect when - the worktree file is changed by something else before git update-index - gets to look at it. - - Asks git to refresh its index information for the file. - That in turn runs the clean filter on the file; when the clean - filter produces the same pointer that was in the index before, git - realizes that the file has not actually been modified. - - Note that, if the pointer file is staged for deletion, or has different - content than the current worktree content staged, this won't change - that. So it's safe to call at any time and any situation. - - If the index is known to be locked (eg, git add has run git-annex), - that would fail. Restage False will prevent the index being updated, - and will store it in the restage log. Displays a message to help the - user understand why the file will appear to be modified. - - This uses the git queue, so the update is not performed immediately, - and this can be run multiple times cheaply. Using the git queue also - prevents building up too large a number of updates when many files - are being processed. It's also recorded in the restage log so that, - if the process is interrupted before the git queue is fulushed, the - restage will be taken care of later. -} restagePointerFile :: Restage -> RawFilePath -> InodeCache -> Annex () restagePointerFile (Restage False) f orig = do flip writeRestageLog orig =<< inRepo (toTopFilePath f) toplevelWarning True $ unableToRestage $ Just $ fromRawFilePath f restagePointerFile (Restage True) f orig = do flip writeRestageLog orig =<< inRepo (toTopFilePath f) -- Avoid refreshing the index if run by the -- smudge clean filter, because git uses that when -- it's already refreshing the index, probably because -- this very action is running. Running it again would likely -- deadlock. unlessM (Annex.getState Annex.insmudgecleanfilter) $ Annex.Queue.addFlushAction restagePointerFileRunner [f] restagePointerFileRunner :: Git.Queue.FlushActionRunner Annex restagePointerFileRunner = Git.Queue.FlushActionRunner "restagePointerFiles" $ \r _fs -> restagePointerFiles r -- Restage all files in the restage log that have not been modified. -- -- Other changes to the files may have been staged before this -- gets a chance to run. To avoid a race with any staging of -- changes, first lock the index file. Then run git update-index -- on all still-unmodified files, using a copy of the index file, -- to bypass the lock. Then replace the old index file with the new -- updated index file. restagePointerFiles :: Git.Repo -> Annex () restagePointerFiles r = unlessM (Annex.getState Annex.insmudgecleanfilter) $ do -- Flush any queued changes to the keys database, so they -- are visible to child processes. -- The database is closed because that may improve behavior -- when run in Windows's WSL1, which has issues with -- multiple writers to SQL databases. liftIO . Database.Keys.Handle.closeDbHandle =<< Annex.getRead Annex.keysdbhandle realindex <- liftIO $ Git.Index.currentIndexFile r numsz@(numfiles, _) <- calcnumsz let lock = fromRawFilePath (Git.Index.indexFileLock realindex) lockindex = liftIO $ catchMaybeIO $ Git.LockFile.openLock' lock unlockindex = liftIO . maybe noop Git.LockFile.closeLock showwarning = warning $ unableToRestage Nothing go Nothing = showwarning go (Just _) = withtmpdir $ \tmpdir -> do tsd <- getTSDelta let tmpindex = toRawFilePath (tmpdir "index") let replaceindex = liftIO $ moveFile tmpindex realindex let updatetmpindex = do r' <- liftIO $ Git.Env.addGitEnv r Git.Index.indexEnv =<< Git.Index.indexEnvVal tmpindex configfilterprocess numsz $ runupdateindex tsd r' replaceindex return True ok <- liftIO (createLinkOrCopy realindex tmpindex) <&&> catchBoolIO updatetmpindex unless ok showwarning when (numfiles > 0) $ bracket lockindex unlockindex go where withtmpdir = withTmpDirIn (fromRawFilePath $ Git.localGitDir r) "annexindex" isunmodified tsd f orig = genInodeCache f tsd >>= return . \case Nothing -> False Just new -> compareStrong orig new {- Avoid git warning about CRLF munging -} avoidcrlfwarning r' = r' { gitGlobalOpts = gitGlobalOpts r' ++ [ Param "-c" , Param $ "core.safecrlf=" ++ boolConfig False ] } runupdateindex tsd r' replaceindex = runsGitAnnexChildProcessViaGit' (avoidcrlfwarning r') $ \r'' -> Git.UpdateIndex.refreshIndex r'' $ \feeder -> do let atend = do -- wait for index write liftIO $ feeder Nothing replaceindex streamRestageLog atend $ \topf ic -> do let f = fromTopFilePath topf r'' liftIO $ whenM (isunmodified tsd f ic) $ feedupdateindex f feeder {- update-index is documented as picky about "./file" and it - fails on "../../repo/path/file" when cwd is not in the repo - being acted on. Avoid these problems with an absolute path. -} feedupdateindex f feeder = do absf <- absPath f feeder (Just absf) calcnumsz = calcRestageLog (0, 0) $ \(_f, ic) (numfiles, sizefiles) -> (numfiles+1, sizefiles + inodeCacheFileSize ic) {- filter.annex.process configured to use git-annex filter-process - is sometimes faster and sometimes slower than using - git-annex smudge. The latter is run once per file, while - the former has the content of files piped to it. -} filterprocessfaster :: (Integer, FileSize) -> Bool filterprocessfaster (numfiles, sizefiles) = let estimate_enabled = sizefiles `div` 191739611 estimate_disabled = numfiles `div` 7 in estimate_enabled <= estimate_disabled {- This disables filter.annex.process if it's set when it would - probably not be faster to use it. Unfortunately, simply - passing -c filter.annex.process= also prevents git from - running the smudge filter, so .git/config has to be modified - to disable it. The modification is reversed at the end. In - case this process is terminated early, the next time this - runs it will take care of reversing the modification. -} configfilterprocess numsz = bracket setup cleanup . const where setup | filterprocessfaster numsz = return Nothing | otherwise = fromRepo (Git.Config.getMaybe ck) >>= \case Nothing -> return Nothing Just v -> do void $ inRepo (Git.Config.change ckd (fromConfigValue v)) void $ inRepo (Git.Config.unset ck) return (Just v) cleanup (Just v) = do void $ inRepo $ Git.Config.change ck (fromConfigValue v) void $ inRepo (Git.Config.unset ckd) cleanup Nothing = fromRepo (Git.Config.getMaybe ckd) >>= \case Nothing -> return () Just v -> do whenM (isNothing <$> fromRepo (Git.Config.getMaybe ck)) $ void $ inRepo (Git.Config.change ck (fromConfigValue v)) void $ inRepo (Git.Config.unset ckd) ck = ConfigKey "filter.annex.process" ckd = ConfigKey "filter.annex.process-temp-disabled" unableToRestage :: Maybe FilePath -> String unableToRestage mf = unwords [ "git status will show " ++ fromMaybe "some files" mf , "to be modified, since content availability has changed" , "and git-annex was unable to update the index." , "This is only a cosmetic problem affecting git status; git add," , "git commit, etc won't be affected." , "To fix the git status display, you can run:" , "git-annex restage" ] {- Parses a symlink target or a pointer file to a Key. - - Makes sure that the pointer file is valid, including not being longer - than the maximum allowed size of a valid pointer file, and that any - subsequent lines after the first contain the validPointerLineTag. - If a valid pointer file gets some other data appended to it, it should - never be considered valid, unless that data happened to itself be a - valid pointer file. -} parseLinkTargetOrPointer :: S.ByteString -> Maybe Key parseLinkTargetOrPointer = either (const Nothing) id . parseLinkTargetOrPointer' data InvalidAppendedPointerFile = InvalidAppendedPointerFile parseLinkTargetOrPointer' :: S.ByteString -> Either InvalidAppendedPointerFile (Maybe Key) parseLinkTargetOrPointer' b = let (firstline, rest) = S8.span (/= '\n') b in case parsekey $ droptrailing '\r' firstline of Just k | S.length b > maxValidPointerSz -> Left InvalidAppendedPointerFile | restvalid (dropleading '\n' rest) -> Right (Just k) | otherwise -> Left InvalidAppendedPointerFile Nothing -> Right Nothing where parsekey l | isLinkToAnnex l = fileKey $ snd $ S8.breakEnd pathsep l | otherwise = Nothing restvalid r | S.null r = True | otherwise = let (l, r') = S8.span (/= '\n') r in validPointerLineTag `S.isInfixOf` l && (not (S8.null r') && S8.head r' == '\n') && restvalid (S8.tail r') dropleading c l | S.null l = l | S8.head l == c = S8.tail l | otherwise = l droptrailing c l | S.null l = l | S8.last l == c = S8.init l | otherwise = l pathsep '/' = True #ifdef mingw32_HOST_OS pathsep '\\' = True #endif pathsep _ = False {- Avoid looking at more of the lazy ByteString than necessary since it - could be reading from a large file that is not a pointer file. -} parseLinkTargetOrPointerLazy :: L.ByteString -> Maybe Key parseLinkTargetOrPointerLazy = either (const Nothing) id . parseLinkTargetOrPointerLazy' parseLinkTargetOrPointerLazy' :: L.ByteString -> Either InvalidAppendedPointerFile (Maybe Key) parseLinkTargetOrPointerLazy' b = let b' = L.take (fromIntegral maxPointerSz) b in parseLinkTargetOrPointer' (L.toStrict b') formatPointer :: Key -> S.ByteString formatPointer k = prefix <> keyFile k <> nl where prefix = toInternalGitPath $ P.pathSeparator `S.cons` objectDir nl = S8.singleton '\n' {- Maximum size of a file that could be a pointer to a key. - Check to avoid buffering really big files in git into - memory when reading files that may be pointers. - - 8192 bytes is plenty for a pointer to a key. This adds some additional - padding to allow for pointer files that have lines of additional data - after the key. - - One additional byte is used to detect when a valid pointer file - got something else appended to it. -} maxPointerSz :: Int maxPointerSz = maxValidPointerSz + 1 {- Maximum size of a valid pointer files is 32kb. -} maxValidPointerSz :: Int maxValidPointerSz = 32768 maxSymlinkSz :: Int maxSymlinkSz = 8192 {- Checks if a worktree file is a pointer to a key. - - Unlocked files whose content is present are not detected by this. - - It's possible, though unlikely, that an annex symlink points to - an object that looks like a pointer file. Or that a non-annex - symlink does. Avoids a false positive in those cases. - -} isPointerFile :: RawFilePath -> IO (Maybe Key) isPointerFile f = catchDefaultIO Nothing $ #if defined(mingw32_HOST_OS) checkcontentfollowssymlinks -- no symlinks supported on windows #else #if MIN_VERSION_unix(2,8,0) bracket (openFd (fromRawFilePath f) ReadOnly (defaultFileFlags { nofollow = True }) Nothing) closeFd (\fd -> readhandle =<< fdToHandle fd) #else ifM (isSymbolicLink <$> R.getSymbolicLinkStatus f) ( return Nothing , checkcontentfollowssymlinks ) #endif #endif where checkcontentfollowssymlinks = withFile (fromRawFilePath f) ReadMode readhandle readhandle h = parseLinkTargetOrPointer <$> S.hGet h maxPointerSz {- Checks a symlink target or pointer file first line to see if it - appears to point to annexed content. - - We only look for paths inside the .git directory, and not at the .git - directory itself, because GIT_DIR may cause a directory name other - than .git to be used. -} isLinkToAnnex :: S.ByteString -> Bool isLinkToAnnex s = p `S.isInfixOf` s #ifdef mingw32_HOST_OS -- '/' is used inside pointer files on Windows, not the native '\' || p' `S.isInfixOf` s #endif where p = P.pathSeparator `S.cons` objectDir #ifdef mingw32_HOST_OS p' = toInternalGitPath p #endif {- String that must appear on every line of a valid pointer file. -} validPointerLineTag :: S.ByteString validPointerLineTag = "/annex/"