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{- git versions
-
- Copyright 2011, 2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Git.Version where
import Common
data GitVersion = GitVersion String Integer
deriving (Eq)
instance Ord GitVersion where
compare (GitVersion _ x) (GitVersion _ y) = compare x y
instance Show GitVersion where
show (GitVersion s _) = s
installed :: IO GitVersion
installed = normalize . extract <$> readProcess "git" ["--version"]
where
extract s = case lines s of
[] -> ""
(l:_) -> unwords $ drop 2 $ words l
{- To compare dotted versions like 1.7.7 and 1.8, they are normalized to
- a somewhat arbitrary integer representation. -}
normalize :: String -> GitVersion
normalize v = GitVersion v $
sum $ mult 1 $ reverse $ extend precision $ take precision $
map readi $ split "." v
where
extend n l = l ++ replicate (n - length l) 0
mult _ [] = []
mult n (x:xs) = (n*x) : mult (n*10^width) xs
readi :: String -> Integer
readi s = case reads s of
((x,_):_) -> x
_ -> 0
precision = 10 -- number of segments of the version to compare
width = length "yyyymmddhhmmss" -- maximum width of a segment
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