112 lines
3.4 KiB
Haskell
112 lines
3.4 KiB
Haskell
{- git-annex links to content
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-
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- On file systems that support them, symlinks are used.
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-
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- On other filesystems, git instead stores the symlink target in a regular
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- file.
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-
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- Copyright 2013 Joey Hess <id@joeyh.name>
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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 Annex.Link where
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import Common.Annex
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import qualified Annex
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import qualified Git.HashObject
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import qualified Git.UpdateIndex
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import qualified Annex.Queue
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import Git.Types
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import Git.FilePath
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type LinkTarget = String
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{- Checks if a file is a link to a key. -}
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isAnnexLink :: FilePath -> Annex (Maybe Key)
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isAnnexLink file = maybe Nothing (fileKey . takeFileName) <$> getAnnexLinkTarget file
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{- Gets the link target of a symlink.
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-
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- On a filesystem that does not support symlinks, fall back to getting the
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- link target by looking inside the file.
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-
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- Returns Nothing if the file is not a symlink, or not a link to annex
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- content.
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-}
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getAnnexLinkTarget :: FilePath -> Annex (Maybe LinkTarget)
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getAnnexLinkTarget f = getAnnexLinkTarget' f
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=<< (coreSymlinks <$> Annex.getGitConfig)
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{- Pass False to force looking inside file. -}
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getAnnexLinkTarget' :: FilePath -> Bool -> Annex (Maybe LinkTarget)
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getAnnexLinkTarget' file coresymlinks = if coresymlinks
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then check readSymbolicLink $
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return Nothing
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else check readSymbolicLink $
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check probefilecontent $
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return Nothing
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where
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check getlinktarget fallback = do
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v <- liftIO $ catchMaybeIO $ getlinktarget file
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case v of
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Just l
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| isLinkToAnnex (fromInternalGitPath l) -> return v
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| otherwise -> return Nothing
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Nothing -> fallback
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probefilecontent f = withFile f ReadMode $ \h -> do
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fileEncoding h
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-- The first 8k is more than enough to read; link
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-- files are small.
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s <- take 8192 <$> hGetContents h
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-- If we got the full 8k, the file is too large
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if length s == 8192
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then return ""
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else
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-- If there are any NUL or newline
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-- characters, or whitespace, we
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-- certianly don't have a link to a
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-- git-annex key.
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return $ if any (`elem` s) "\0\n\r \t"
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then ""
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else s
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makeAnnexLink :: LinkTarget -> FilePath -> Annex ()
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makeAnnexLink = makeGitLink
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{- Creates a link on disk.
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-
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- On a filesystem that does not support symlinks, writes the link target
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- to a file. Note that git will only treat the file as a symlink if
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- it's staged as such, so use addAnnexLink when adding a new file or
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- modified link to git.
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-}
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makeGitLink :: LinkTarget -> FilePath -> Annex ()
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makeGitLink linktarget file = ifM (coreSymlinks <$> Annex.getGitConfig)
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( liftIO $ do
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void $ tryIO $ removeFile file
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createSymbolicLink linktarget file
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, liftIO $ writeFile file linktarget
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)
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{- Creates a link on disk, and additionally stages it in git. -}
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addAnnexLink :: LinkTarget -> FilePath -> Annex ()
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addAnnexLink linktarget file = do
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makeAnnexLink linktarget file
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stageSymlink file =<< hashSymlink linktarget
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{- Injects a symlink target into git, returning its Sha. -}
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hashSymlink :: LinkTarget -> Annex Sha
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hashSymlink linktarget = inRepo $ Git.HashObject.hashObject BlobObject $
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toInternalGitPath linktarget
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hashSymlink' :: Git.HashObject.HashObjectHandle -> LinkTarget -> Annex Sha
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hashSymlink' h linktarget = liftIO $ Git.HashObject.hashBlob h $
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toInternalGitPath linktarget
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{- Stages a symlink to the annex, using a Sha of its target. -}
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stageSymlink :: FilePath -> Sha -> Annex ()
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stageSymlink file sha =
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Annex.Queue.addUpdateIndex =<<
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inRepo (Git.UpdateIndex.stageSymlink file sha)
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