From 471aa27bf0a0e4c698303acb7fdf9cea6a75634b Mon Sep 17 00:00:00 2001
From: Joey Hess <joey@kitenet.net>
Date: Mon, 18 Nov 2013 13:06:58 -0400
Subject: copied from git-annex

---
 Git/Version.hs | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 Git/Version.hs

(limited to 'Git/Version.hs')

diff --git a/Git/Version.hs b/Git/Version.hs
new file mode 100644
index 0000000..5ad1d59
--- /dev/null
+++ b/Git/Version.hs
@@ -0,0 +1,43 @@
+{- 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
-- 
cgit v1.2.3