better git version checking

Git/BuildVersion.hs

@@ -0,0 +1,21 @@
+{- git build version
+ -
+ - Copyright 2011 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Git.BuildVersion where
+
+import Git.Version
+import qualified Build.SysConfig
+
+{- Using the version it was configured for avoids running git to check its
+ - version, at the cost that upgrading git won't be noticed.
+ - This is only acceptable because it's rare that git's version influences
+ - code's behavior. -}
+buildVersion :: GitVersion
+buildVersion = normalize Build.SysConfig.gitversion
+
+older :: String -> Bool
+older n = buildVersion < normalize n