git-annex/Git.hs
Joey Hess 9290095fc2 improve type signatures with a Ref newtype
In git, a Ref can be a Sha, or a Branch, or a Tag. I added type aliases for
those. Note that this does not prevent mixing up of eg, refs and branches
at the type level. Since git really doesn't care, except rare cases like
git update-ref, or git tag -d, that seems ok for now.

There's also a tree-ish, but let's just use Ref for it. A given Sha or Ref
may or may not be a tree-ish, depending on the object type, so there seems
no point in trying to represent it at the type level.
2011-11-16 02:41:46 -04:00

744 lines
22 KiB
Haskell

{- git repository handling
-
- This is written to be completely independant of git-annex and should be
- suitable for other uses.
-
- Copyright 2010,2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Git (
Repo,
Ref(..),
Branch,
Sha,
Tag,
repoFromCwd,
repoFromAbsPath,
repoFromUnknown,
repoFromUrl,
localToUrl,
repoIsUrl,
repoIsSsh,
repoIsHttp,
repoIsLocalBare,
repoDescribe,
refDescribe,
repoLocation,
workTree,
workTreeFile,
gitDir,
urlPath,
urlHost,
urlPort,
urlHostUser,
urlAuthority,
urlScheme,
configGet,
configMap,
configRead,
hConfigRead,
configStore,
configTrue,
gitCommandLine,
run,
runBool,
pipeRead,
pipeWrite,
pipeWriteRead,
pipeNullSplit,
pipeNullSplitB,
attributes,
remotes,
remotesAdd,
genRemote,
repoRemoteName,
repoRemoteNameSet,
repoRemoteNameFromKey,
checkAttr,
decodeGitFile,
encodeGitFile,
repoAbsPath,
reap,
useIndex,
getSha,
shaSize,
commit,
assertLocal,
prop_idempotent_deencode
) where
import System.Posix.Directory
import System.Posix.User
import IO (bracket_, try)
import qualified Data.Map as M hiding (map, split)
import Network.URI
import Data.Char
import Data.Word (Word8)
import Codec.Binary.UTF8.String (encode)
import Text.Printf
import System.Exit
import System.Posix.Env (setEnv, unsetEnv, getEnv)
import qualified Data.ByteString.Lazy.Char8 as L
import Common
{- There are two types of repositories; those on local disk and those
- accessed via an URL. -}
data RepoLocation = Dir FilePath | Url URI | Unknown
deriving (Show, Eq)
data Repo = Repo {
location :: RepoLocation,
config :: M.Map String String,
remotes :: [Repo],
-- remoteName holds the name used for this repo in remotes
remoteName :: Maybe String
} deriving (Show, Eq)
{- A git ref. Can be a sha1, or a branch or tag name. -}
newtype Ref = Ref String
deriving (Eq)
instance Show Ref where
show (Ref v) = v
{- Aliases for Ref. -}
type Branch = Ref
type Sha = Ref
type Tag = Ref
newFrom :: RepoLocation -> Repo
newFrom l =
Repo {
location = l,
config = M.empty,
remotes = [],
remoteName = Nothing
}
{- Local Repo constructor, requires an absolute path to the repo be
- specified. -}
repoFromAbsPath :: FilePath -> IO Repo
repoFromAbsPath dir
| "/" `isPrefixOf` dir = do
-- Git always looks for "dir.git" in preference to
-- to "dir", even if dir ends in a "/".
let canondir = dropTrailingPathSeparator dir
let dir' = canondir ++ ".git"
e <- doesDirectoryExist dir'
if e
then ret dir'
else if "/.git" `isSuffixOf` canondir
then do
-- When dir == "foo/.git", git looks
-- for "foo/.git/.git", and failing
-- that, uses "foo" as the repository.
e' <- doesDirectoryExist $ dir </> ".git"
if e'
then ret dir
else ret $ takeDirectory canondir
else ret dir
| otherwise = error $ "internal error, " ++ dir ++ " is not absolute"
where
ret = return . newFrom . Dir
{- Remote Repo constructor. Throws exception on invalid url. -}
repoFromUrl :: String -> IO Repo
repoFromUrl url
| startswith "file://" url = repoFromAbsPath $ uriPath u
| otherwise = return $ newFrom $ Url u
where
u = fromMaybe bad $ parseURI url
bad = error $ "bad url " ++ url
{- Creates a repo that has an unknown location. -}
repoFromUnknown :: Repo
repoFromUnknown = newFrom Unknown
{- Converts a Local Repo into a remote repo, using the reference repo
- which is assumed to be on the same host. -}
localToUrl :: Repo -> Repo -> Repo
localToUrl reference r
| not $ repoIsUrl reference = error "internal error; reference repo not url"
| repoIsUrl r = r
| otherwise = r { location = Url $ fromJust $ parseURI absurl }
where
absurl =
urlScheme reference ++ "//" ++
urlAuthority reference ++
workTree r
{- User-visible description of a git repo. -}
repoDescribe :: Repo -> String
repoDescribe Repo { remoteName = Just name } = name
repoDescribe Repo { location = Url url } = show url
repoDescribe Repo { location = Dir dir } = dir
repoDescribe Repo { location = Unknown } = "UNKNOWN"
{- Converts a fully qualified git ref into a user-visible version. -}
refDescribe :: Ref -> String
refDescribe = remove "refs/heads/" . remove "refs/remotes/" . show
where
remove prefix s
| prefix `isPrefixOf` s = drop (length prefix) s
| otherwise = s
{- Location of the repo, either as a path or url. -}
repoLocation :: Repo -> String
repoLocation Repo { location = Url url } = show url
repoLocation Repo { location = Dir dir } = dir
repoLocation Repo { location = Unknown } = undefined
{- Constructs and returns an updated version of a repo with
- different remotes list. -}
remotesAdd :: Repo -> [Repo] -> Repo
remotesAdd repo rs = repo { remotes = rs }
{- Returns the name of the remote that corresponds to the repo, if
- it is a remote. -}
repoRemoteName :: Repo -> Maybe String
repoRemoteName Repo { remoteName = Just name } = Just name
repoRemoteName _ = Nothing
{- Sets the name of a remote. -}
repoRemoteNameSet :: String -> Repo -> Repo
repoRemoteNameSet n r = r { remoteName = Just n }
{- Sets the name of a remote based on the git config key, such as
"remote.foo.url". -}
repoRemoteNameFromKey :: String -> Repo -> Repo
repoRemoteNameFromKey k = repoRemoteNameSet basename
where
basename = join "." $ reverse $ drop 1 $
reverse $ drop 1 $ split "." k
{- Some code needs to vary between URL and normal repos,
- or bare and non-bare, these functions help with that. -}
repoIsUrl :: Repo -> Bool
repoIsUrl Repo { location = Url _ } = True
repoIsUrl _ = False
repoIsSsh :: Repo -> Bool
repoIsSsh Repo { location = Url url }
| uriScheme url == "ssh:" = True
-- git treats these the same as ssh
| uriScheme url == "git+ssh:" = True
| uriScheme url == "ssh+git:" = True
| otherwise = False
repoIsSsh _ = False
repoIsHttp :: Repo -> Bool
repoIsHttp Repo { location = Url url }
| uriScheme url == "http:" = True
| uriScheme url == "https:" = True
| otherwise = False
repoIsHttp _ = False
configAvail ::Repo -> Bool
configAvail Repo { config = c } = c /= M.empty
repoIsLocalBare :: Repo -> Bool
repoIsLocalBare r@(Repo { location = Dir _ }) = configAvail r && configBare r
repoIsLocalBare _ = False
assertLocal :: Repo -> a -> a
assertLocal repo action =
if not $ repoIsUrl repo
then action
else error $ "acting on URL git repo " ++ repoDescribe repo ++
" not supported"
assertUrl :: Repo -> a -> a
assertUrl repo action =
if repoIsUrl repo
then action
else error $ "acting on local git repo " ++ repoDescribe repo ++
" not supported"
configBare :: Repo -> Bool
configBare repo = maybe unknown configTrue $ M.lookup "core.bare" $ config repo
where
unknown = error $ "it is not known if git repo " ++
repoDescribe repo ++
" is a bare repository; config not read"
{- Path to a repository's gitattributes file. -}
attributes :: Repo -> String
attributes repo
| configBare repo = workTree repo ++ "/info/.gitattributes"
| otherwise = workTree repo ++ "/.gitattributes"
{- Path to a repository's .git directory. -}
gitDir :: Repo -> String
gitDir repo
| configBare repo = workTree repo
| otherwise = workTree repo </> ".git"
{- Path to a repository's --work-tree, that is, its top.
-
- Note that for URL repositories, this is the path on the remote host. -}
workTree :: Repo -> FilePath
workTree r@(Repo { location = Url _ }) = urlPath r
workTree (Repo { location = Dir d }) = d
workTree Repo { location = Unknown } = undefined
{- Given a relative or absolute filename inside a git repository's
- workTree, calculates the name to use to refer to that file to git.
-
- This is complicated because the best choice can vary depending on
- whether the cwd is in a subdirectory of the git repository, or not.
-
- For example, when adding a file "/tmp/repo/foo", it's best to refer
- to it as "foo" if the cwd is outside the repository entirely
- (this avoids a gotcha with using the full path name when /tmp/repo
- is itself a symlink). But, if the cwd is "/tmp/repo/subdir",
- it's best to refer to "../foo".
-}
workTreeFile :: FilePath -> Repo -> IO FilePath
workTreeFile file repo@(Repo { location = Dir d }) = do
cwd <- getCurrentDirectory
let file' = absfile cwd
unless (inrepo file') $
error $ file ++ " is not located inside git repository " ++ absrepo
if inrepo $ addTrailingPathSeparator cwd
then return $ relPathDirToFile cwd file'
else return $ drop (length absrepo) file'
where
-- normalize both repo and file, so that repo
-- will be substring of file
absrepo = maybe bad addTrailingPathSeparator $ absNormPath "/" d
absfile c = fromMaybe file $ secureAbsNormPath c file
inrepo f = absrepo `isPrefixOf` f
bad = error $ "bad repo" ++ repoDescribe repo
workTreeFile _ repo = assertLocal repo $ error "internal"
{- Path of an URL repo. -}
urlPath :: Repo -> String
urlPath Repo { location = Url u } = uriPath u
urlPath repo = assertUrl repo $ error "internal"
{- Scheme of an URL repo. -}
urlScheme :: Repo -> String
urlScheme Repo { location = Url u } = uriScheme u
urlScheme repo = assertUrl repo $ error "internal"
{- Work around a bug in the real uriRegName
- <http://trac.haskell.org/network/ticket/40> -}
uriRegName' :: URIAuth -> String
uriRegName' a = fixup $ uriRegName a
where
fixup x@('[':rest)
| rest !! len == ']' = take len rest
| otherwise = x
where
len = length rest - 1
fixup x = x
{- Hostname of an URL repo. -}
urlHost :: Repo -> String
urlHost = urlAuthPart uriRegName'
{- Port of an URL repo, if it has a nonstandard one. -}
urlPort :: Repo -> Maybe Integer
urlPort r =
case urlAuthPart uriPort r of
":" -> Nothing
(':':p) -> Just (read p)
_ -> Nothing
{- Hostname of an URL repo, including any username (ie, "user@host") -}
urlHostUser :: Repo -> String
urlHostUser r = urlAuthPart uriUserInfo r ++ urlAuthPart uriRegName' r
{- The full authority portion an URL repo. (ie, "user@host:port") -}
urlAuthority :: Repo -> String
urlAuthority = urlAuthPart assemble
where
assemble a = uriUserInfo a ++ uriRegName' a ++ uriPort a
{- Applies a function to extract part of the uriAuthority of an URL repo. -}
urlAuthPart :: (URIAuth -> a) -> Repo -> a
urlAuthPart a Repo { location = Url u } = a auth
where
auth = fromMaybe (error $ "bad url " ++ show u) (uriAuthority u)
urlAuthPart _ repo = assertUrl repo $ error "internal"
{- Constructs a git command line operating on the specified repo. -}
gitCommandLine :: [CommandParam] -> Repo -> [CommandParam]
gitCommandLine params repo@(Repo { location = Dir _ } ) =
-- force use of specified repo via --git-dir and --work-tree
[ Param ("--git-dir=" ++ gitDir repo)
, Param ("--work-tree=" ++ workTree repo)
] ++ params
gitCommandLine _ repo = assertLocal repo $ error "internal"
{- Runs git in the specified repo. -}
runBool :: String -> [CommandParam] -> Repo -> IO Bool
runBool subcommand params repo = assertLocal repo $
boolSystem "git" $ gitCommandLine (Param subcommand : params) repo
{- Runs git in the specified repo, throwing an error if it fails. -}
run :: String -> [CommandParam] -> Repo -> IO ()
run subcommand params repo = assertLocal repo $
runBool subcommand params repo
>>! error $ "git " ++ show params ++ " failed"
{- Runs a git subcommand and returns its output, lazily.
-
- Note that this leaves the git process running, and so zombies will
- result unless reap is called.
-}
pipeRead :: [CommandParam] -> Repo -> IO L.ByteString
pipeRead params repo = assertLocal repo $ do
(_, h) <- hPipeFrom "git" $ toCommand $ gitCommandLine params repo
hSetBinaryMode h True
L.hGetContents h
{- Runs a git subcommand, feeding it input.
- You should call either getProcessStatus or forceSuccess on the PipeHandle. -}
pipeWrite :: [CommandParam] -> L.ByteString -> Repo -> IO PipeHandle
pipeWrite params s repo = assertLocal repo $ do
(p, h) <- hPipeTo "git" (toCommand $ gitCommandLine params repo)
L.hPut h s
hClose h
return p
{- Runs a git subcommand, feeding it input, and returning its output.
- You should call either getProcessStatus or forceSuccess on the PipeHandle. -}
pipeWriteRead :: [CommandParam] -> L.ByteString -> Repo -> IO (PipeHandle, L.ByteString)
pipeWriteRead params s repo = assertLocal repo $ do
(p, from, to) <- hPipeBoth "git" (toCommand $ gitCommandLine params repo)
hSetBinaryMode from True
L.hPut to s
hClose to
c <- L.hGetContents from
return (p, c)
{- Reads null terminated output of a git command (as enabled by the -z
- parameter), and splits it. -}
pipeNullSplit :: [CommandParam] -> Repo -> IO [String]
pipeNullSplit params repo = map L.unpack <$> pipeNullSplitB params repo
{- For when Strings are not needed. -}
pipeNullSplitB ::[CommandParam] -> Repo -> IO [L.ByteString]
pipeNullSplitB params repo = filter (not . L.null) . L.split '\0' <$>
pipeRead params repo
{- Reaps any zombie git processes. -}
reap :: IO ()
reap = do
-- throws an exception when there are no child processes
r <- catchDefaultIO (getAnyProcessStatus False True) Nothing
maybe (return ()) (const reap) r
{- Forces git to use the specified index file.
- Returns an action that will reset back to the default
- index file. -}
useIndex :: FilePath -> IO (IO ())
useIndex index = do
res <- try $ getEnv var
setEnv var index True
return $ reset res
where
var = "GIT_INDEX_FILE"
reset (Right (Just v)) = setEnv var v True
reset _ = unsetEnv var
{- Runs an action that causes a git subcommand to emit a sha, and strips
any trailing newline, returning the sha. -}
getSha :: String -> IO String -> IO Sha
getSha subcommand a = do
t <- a
let t' = if last t == '\n'
then init t
else t
when (length t' /= shaSize) $
error $ "failed to read sha from git " ++ subcommand ++ " (" ++ t' ++ ")"
return $ Ref t'
{- Size of a git sha. -}
shaSize :: Int
shaSize = 40
{- Commits the index into the specified branch (or other ref),
- with the specified parent refs. -}
commit :: String -> Ref -> [Ref] -> Repo -> IO ()
commit message newref parentrefs repo = do
tree <- getSha "write-tree" $ asString $
pipeRead [Param "write-tree"] repo
sha <- getSha "commit-tree" $ asString $
ignorehandle $ pipeWriteRead
(map Param $ ["commit-tree", show tree] ++ ps)
(L.pack message) repo
run "update-ref" [Param $ show newref, Param $ show sha] repo
where
ignorehandle a = snd <$> a
asString a = L.unpack <$> a
ps = concatMap (\r -> ["-p", show r]) parentrefs
{- Runs git config and populates a repo with its config. -}
configRead :: Repo -> IO Repo
configRead repo@(Repo { location = Dir d }) = do
{- Cannot use pipeRead because it relies on the config having
been already read. Instead, chdir to the repo. -}
cwd <- getCurrentDirectory
bracket_ (changeWorkingDirectory d)
(\_ -> changeWorkingDirectory cwd) $
pOpen ReadFromPipe "git" ["config", "--list"] $
hConfigRead repo
configRead r = assertLocal r $ error "internal"
{- Reads git config from a handle and populates a repo with it. -}
hConfigRead :: Repo -> Handle -> IO Repo
hConfigRead repo h = do
val <- hGetContentsStrict h
configStore val repo
{- Stores a git config into a repo, returning the new version of the repo.
- The git config may be multiple lines, or a single line. Config settings
- can be updated inrementally. -}
configStore :: String -> Repo -> IO Repo
configStore s repo = do
let repo' = repo { config = configParse s `M.union` config repo }
rs <- configRemotes repo'
return $ repo' { remotes = rs }
{- Parses git config --list output into a config map. -}
configParse :: String -> M.Map String String
configParse s = M.fromList $ map pair $ lines s
where
pair l = (key l, val l)
key l = head $ keyval l
val l = join sep $ drop 1 $ keyval l
keyval l = split sep l :: [String]
sep = "="
{- Calculates a list of a repo's configured remotes, by parsing its config. -}
configRemotes :: Repo -> IO [Repo]
configRemotes repo = mapM construct remotepairs
where
filterconfig f = filter f $ M.toList $ config repo
filterkeys f = filterconfig (\(k,_) -> f k)
remotepairs = filterkeys isremote
isremote k = startswith "remote." k && endswith ".url" k
construct (k,v) = repoRemoteNameFromKey k <$> genRemote v repo
{- Generates one of a repo's remotes using a given location (ie, an url). -}
genRemote :: String -> Repo -> IO Repo
genRemote s repo = gen $ calcloc s
where
filterconfig f = filter f $ M.toList $ config repo
gen v
| scpstyle v = repoFromUrl $ scptourl v
| isURI v = repoFromUrl v
| otherwise = repoFromRemotePath v repo
-- insteadof config can rewrite remote location
calcloc l
| null insteadofs = l
| otherwise = replacement ++ drop (length bestvalue) l
where
replacement = drop (length prefix) $
take (length bestkey - length suffix) bestkey
(bestkey, bestvalue) = maximumBy longestvalue insteadofs
longestvalue (_, a) (_, b) = compare b a
insteadofs = filterconfig $ \(k, v) ->
startswith prefix k &&
endswith suffix k &&
startswith v l
(prefix, suffix) = ("url." , ".insteadof")
-- git remotes can be written scp style -- [user@]host:dir
scpstyle v = ":" `isInfixOf` v && not ("//" `isInfixOf` v)
scptourl v = "ssh://" ++ host ++ slash dir
where
bits = split ":" v
host = head bits
dir = join ":" $ drop 1 bits
slash d | d == "" = "/~/" ++ dir
| head d == '/' = dir
| head d == '~' = '/':dir
| otherwise = "/~/" ++ dir
{- Checks if a string from git config is a true value. -}
configTrue :: String -> Bool
configTrue s = map toLower s == "true"
{- Returns a single git config setting, or a default value if not set. -}
configGet :: String -> String -> Repo -> String
configGet key defaultValue repo =
M.findWithDefault defaultValue key (config repo)
{- Access to raw config Map -}
configMap :: Repo -> M.Map String String
configMap = config
{- Efficiently looks up a gitattributes value for each file in a list. -}
checkAttr :: String -> [FilePath] -> Repo -> IO [(FilePath, String)]
checkAttr attr files repo = do
-- git check-attr needs relative filenames input; it will choke
-- on some absolute filenames. This also means it will output
-- all relative filenames.
cwd <- getCurrentDirectory
let relfiles = map (relPathDirToFile cwd . absPathFrom cwd) files
(_, fromh, toh) <- hPipeBoth "git" (toCommand params)
_ <- forkProcess $ do
hClose fromh
hPutStr toh $ join "\0" relfiles
hClose toh
exitSuccess
hClose toh
(map topair . lines) <$> hGetContents fromh
where
params = gitCommandLine
[ Param "check-attr"
, Param attr
, Params "-z --stdin"
] repo
topair l = (file, value)
where
file = decodeGitFile $ join sep $ take end bits
value = bits !! end
end = length bits - 1
bits = split sep l
sep = ": " ++ attr ++ ": "
{- Some git commands output encoded filenames. Decode that (annoyingly
- complex) encoding. -}
decodeGitFile :: String -> FilePath
decodeGitFile [] = []
decodeGitFile f@(c:s)
-- encoded strings will be inside double quotes
| c == '"' = unescape ("", middle)
| otherwise = f
where
e = '\\'
middle = init s
unescape (b, []) = b
-- look for escapes starting with '\'
unescape (b, v) = b ++ beginning ++ unescape (decode rest)
where
pair = span (/= e) v
beginning = fst pair
rest = snd pair
isescape x = x == e
-- \NNN is an octal encoded character
decode (x:n1:n2:n3:rest)
| isescape x && alloctal = (fromoctal, rest)
where
alloctal = isOctDigit n1 &&
isOctDigit n2 &&
isOctDigit n3
fromoctal = [chr $ readoctal [n1, n2, n3]]
readoctal o = read $ "0o" ++ o :: Int
-- \C is used for a few special characters
decode (x:nc:rest)
| isescape x = ([echar nc], rest)
where
echar 'a' = '\a'
echar 'b' = '\b'
echar 'f' = '\f'
echar 'n' = '\n'
echar 'r' = '\r'
echar 't' = '\t'
echar 'v' = '\v'
echar a = a
decode n = ("", n)
{- Should not need to use this, except for testing decodeGitFile. -}
encodeGitFile :: FilePath -> String
encodeGitFile s = foldl (++) "\"" (map echar s) ++ "\""
where
e c = '\\' : [c]
echar '\a' = e 'a'
echar '\b' = e 'b'
echar '\f' = e 'f'
echar '\n' = e 'n'
echar '\r' = e 'r'
echar '\t' = e 't'
echar '\v' = e 'v'
echar '\\' = e '\\'
echar '"' = e '"'
echar x
| ord x < 0x20 = e_num x -- low ascii
| ord x >= 256 = e_utf x
| ord x > 0x7E = e_num x -- high ascii
| otherwise = [x] -- printable ascii
where
showoctal i = '\\' : printf "%03o" i
e_num c = showoctal $ ord c
-- unicode character is decomposed to
-- Word8s and each is shown in octal
e_utf c = showoctal =<< (encode [c] :: [Word8])
{- for quickcheck -}
prop_idempotent_deencode :: String -> Bool
prop_idempotent_deencode s = s == decodeGitFile (encodeGitFile s)
{- Constructs a Repo from the path specified in the git remotes of
- another Repo. -}
repoFromRemotePath :: FilePath -> Repo -> IO Repo
repoFromRemotePath dir repo = do
dir' <- expandTilde dir
repoFromAbsPath $ workTree repo </> dir'
{- Git remotes can have a directory that is specified relative
- to the user's home directory, or that contains tilde expansions.
- This converts such a directory to an absolute path.
- Note that it has to run on the system where the remote is.
-}
repoAbsPath :: FilePath -> IO FilePath
repoAbsPath d = do
d' <- expandTilde d
h <- myHomeDir
return $ h </> d'
expandTilde :: FilePath -> IO FilePath
expandTilde = expandt True
where
expandt _ [] = return ""
expandt _ ('/':cs) = do
v <- expandt True cs
return ('/':v)
expandt True ('~':'/':cs) = do
h <- myHomeDir
return $ h </> cs
expandt True ('~':cs) = do
let (name, rest) = findname "" cs
u <- getUserEntryForName name
return $ homeDirectory u </> rest
expandt _ (c:cs) = do
v <- expandt False cs
return (c:v)
findname n [] = (n, "")
findname n (c:cs)
| c == '/' = (n, cs)
| otherwise = findname (n++[c]) cs
{- Finds the current git repository, which may be in a parent directory. -}
repoFromCwd :: IO Repo
repoFromCwd = getCurrentDirectory >>= seekUp isRepoTop >>= maybe norepo makerepo
where
makerepo = return . newFrom . Dir
norepo = error "Not in a git repository."
seekUp :: (FilePath -> IO Bool) -> FilePath -> IO (Maybe FilePath)
seekUp want dir = do
ok <- want dir
if ok
then return $ Just dir
else case parentDir dir of
"" -> return Nothing
d -> seekUp want d
isRepoTop :: FilePath -> IO Bool
isRepoTop dir = do
r <- isRepo
b <- isBareRepo
return (r || b)
where
isRepo = gitSignature ".git" ".git/config"
isBareRepo = gitSignature "objects" "config"
gitSignature subdir file = liftM2 (&&)
(doesDirectoryExist (dir ++ "/" ++ subdir))
(doesFileExist (dir ++ "/" ++ file))