git-annex/Annex/Link.hs
Joey Hess ba42b67c70 Fix bug in automatic merge conflict resolution
When one side is an annexed symlink, and the other side is a non-annexed symlink.

In this case, git-merge does not replace the annexed symlink in the work
tree with the non-annexed symlink, which is different from it's handling of
conflicts between annexed symlinks and regular files or directories.
So, while git-annex generated the correct merge commit, the work tree
didn't get updated to reflect it.
See comments on bug for additional analysis.

Did not add this to the test suite yet; just unloaded a truckload of firewood
and am feeling lazy.

This commit was sponsored by Adam Spiers.
2014-07-08 13:55:11 -04:00

108 lines
3.2 KiB
Haskell

{- 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.
-
- Copyright 2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Annex.Link where
import Common.Annex
import qualified Annex
import qualified Git.HashObject
import qualified Git.UpdateIndex
import qualified Annex.Queue
import Git.Types
import Git.FilePath
type LinkTarget = String
{- Checks if a file is a link to a key. -}
isAnnexLink :: FilePath -> Annex (Maybe Key)
isAnnexLink file = maybe Nothing (fileKey . takeFileName) <$> getAnnexLinkTarget file
{- Gets the link target of a symlink.
-
- On a filesystem that does not support symlinks, fall back to getting the
- link target by looking inside the file.
-
- Returns Nothing if the file is not a symlink, or not a link to annex
- content.
-}
getAnnexLinkTarget :: FilePath -> Annex (Maybe LinkTarget)
getAnnexLinkTarget file = ifM (coreSymlinks <$> Annex.getGitConfig)
( check readSymbolicLink $
return Nothing
, check readSymbolicLink $
check probefilecontent $
return Nothing
)
where
check getlinktarget fallback = do
v <- liftIO $ catchMaybeIO $ getlinktarget file
case v of
Just l
| isLinkToAnnex (fromInternalGitPath l) -> return v
| otherwise -> return Nothing
Nothing -> fallback
probefilecontent f = withFile f ReadMode $ \h -> do
fileEncoding h
-- The first 8k is more than enough to read; link
-- files are small.
s <- take 8192 <$> hGetContents h
-- If we got the full 8k, the file is too large
if length s == 8192
then return ""
else
-- If there are any NUL or newline
-- characters, or whitespace, we
-- certianly don't have a link to a
-- git-annex key.
return $ if any (`elem` s) "\0\n\r \t"
then ""
else s
makeAnnexLink :: LinkTarget -> FilePath -> 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 -> FilePath -> Annex ()
makeGitLink linktarget file = ifM (coreSymlinks <$> Annex.getGitConfig)
( liftIO $ do
void $ tryIO $ removeFile file
createSymbolicLink linktarget file
, liftIO $ writeFile file linktarget
)
{- Creates a link on disk, and additionally stages it in git. -}
addAnnexLink :: LinkTarget -> FilePath -> 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 linktarget = inRepo $ Git.HashObject.hashObject BlobObject $
toInternalGitPath linktarget
hashSymlink' :: Git.HashObject.HashObjectHandle -> LinkTarget -> Annex Sha
hashSymlink' h linktarget = liftIO $ Git.HashObject.hashBlob h $
toInternalGitPath linktarget
{- Stages a symlink to the annex, using a Sha of its target. -}
stageSymlink :: FilePath -> Sha -> Annex ()
stageSymlink file sha =
Annex.Queue.addUpdateIndex =<<
inRepo (Git.UpdateIndex.stageSymlink file sha)