git-annex/Git/Ref.hs

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{- git ref stuff
-
- Copyright 2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Git.Ref where
import Common
import Git
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import Git.Command
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import Data.Char (chr)
{- Converts a fully qualified git ref into a user-visible string. -}
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describe :: Ref -> String
describe = show . base
{- Often git refs are fully qualified (eg: refs/heads/master).
- Converts such a fully qualified ref into a base ref (eg: master). -}
base :: Ref -> Ref
base = Ref . remove "refs/heads/" . remove "refs/remotes/" . show
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where
remove prefix s
| prefix `isPrefixOf` s = drop (length prefix) s
| otherwise = s
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{- Given a directory such as "refs/remotes/origin", and a ref such as
- refs/heads/master, yields a version of that ref under the directory,
- such as refs/remotes/origin/master. -}
under :: String -> Ref -> Ref
under dir r = Ref $ dir </> show (base r)
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{- Checks if a ref exists. -}
exists :: Ref -> Repo -> IO Bool
exists ref = runBool "show-ref"
[Param "--verify", Param "-q", Param $ show ref]
{- Checks if HEAD exists. It generally will, except for in a repository
- that was just created. -}
headExists :: Repo -> IO Bool
headExists repo = do
ls <- lines <$> pipeReadStrict [Param "show-ref", Param "--head"] repo
return $ any (" HEAD" `isSuffixOf`) ls
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{- Get the sha of a fully qualified git ref, if it exists. -}
sha :: Branch -> Repo -> IO (Maybe Sha)
support all filename encodings with ghc 7.4 Under ghc 7.4, this seems to be able to handle all filename encodings again. Including filename encodings that do not match the LANG setting. I think this will not work with earlier versions of ghc, it uses some ghc internals. Turns out that ghc 7.4 has a special filesystem encoding that it uses when reading/writing filenames (as FilePaths). This encoding is documented to allow "arbitrary undecodable bytes to be round-tripped through it". So, to get FilePaths from eg, git ls-files, set the Handle that is reading from git to use this encoding. Then things basically just work. However, I have not found a way to make Text read using this encoding. Text really does assume unicode. So I had to switch back to using String when reading/writing data to git. Which is a pity, because it's some percent slower, but at least it works. Note that stdout and stderr also have to be set to this encoding, or printing out filenames that contain undecodable bytes causes a crash. IMHO this is a misfeature in ghc, that the user can pass you a filename, which you can readFile, etc, but that default, putStr of filename may cause a crash! Git.CheckAttr gave me special trouble, because the filenames I got back from git, after feeding them in, had further encoding breakage. Rather than try to deal with that, I just zip up the input filenames with the attributes. Which must be returned in the same order queried for this to work. Also of note is an apparent GHC bug I worked around in Git.CheckAttr. It used to forkProcess and feed git from the child process. Unfortunatly, after this forkProcess, accessing the `files` variable from the parent returns []. Not the value that was passed into the function. This screams of a bad bug, that's clobbering a variable, but for now I just avoid forkProcess there to work around it. That forkProcess was itself only added because of a ghc bug, #624389. I've confirmed that the test case for that bug doesn't reproduce it with ghc 7.4. So that's ok, except for the new ghc bug I have not isolated and reported. Why does this simple bit of code magnet the ghc bugs? :) Also, the symlink touching code is currently broken, when used on utf-8 filenames in a non-utf-8 locale, or probably on any filename containing undecodable bytes, and I temporarily commented it out.
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sha branch repo = process <$> showref repo
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where
showref = pipeReadStrict [Param "show-ref",
Param "--hash", -- get the hash
Param $ show branch]
process [] = Nothing
process s = Just $ Ref $ firstLine s
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{- List of (refs, branches) matching a given ref spec. -}
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matching :: Ref -> Repo -> IO [(Ref, Branch)]
matching ref repo = map gen . lines <$>
pipeReadStrict [Param "show-ref", Param $ show ref] repo
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where
gen l = let (r, b) = separate (== ' ') l
in (Ref r, Ref b)
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{- List of (refs, branches) matching a given ref spec.
- Duplicate refs are filtered out. -}
matchingUniq :: Ref -> Repo -> IO [(Ref, Branch)]
matchingUniq ref repo = nubBy uniqref <$> matching ref repo
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where
uniqref (a, _) (b, _) = a == b
{- Checks if a String is a legal git ref name.
-
- The rules for this are complex; see git-check-ref-format(1) -}
legal :: Bool -> String -> Bool
legal allowonelevel s = all (== False) illegal
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where
illegal =
[ any ("." `isPrefixOf`) pathbits
, any (".lock" `isSuffixOf`) pathbits
, not allowonelevel && length pathbits < 2
, contains ".."
, any (\c -> contains [c]) illegalchars
, begins "/"
, ends "/"
, contains "//"
, ends "."
, contains "@{"
, null s
]
contains v = v `isInfixOf` s
ends v = v `isSuffixOf` s
begins v = v `isPrefixOf` s
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pathbits = split "/" s
illegalchars = " ~^:?*[\\" ++ controlchars
controlchars = chr 0o177 : [chr 0 .. chr (0o40-1)]