unused: Add --used option, which can specify a set of refs to consider used, rather than the default of considering all refs used.

Types/RefSpec.hs

@@ -0,0 +1,44 @@
+{- This is not the same as git's fetch/push refspecs.
+ - 
+ - Copyright 2015 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Types.RefSpec where
+
+import Common
+import Utility.Glob
+import Git.Types
+
+import Data.Either
+
+type RefSpec = [RefSpecPart]
+
+data RefSpecPart = AddRef Ref | AddMatching Glob | RemoveMatching Glob
+
+allRefSpec :: RefSpec
+allRefSpec = [AddMatching $ compileGlob "*" CaseSensative]
+
+parseRefSpec :: String -> Either String RefSpec
+parseRefSpec v = case partitionEithers (map mk $ split ":" v) of
+	([],refspec) -> Right refspec
+	(e:_,_) -> Left e
+  where
+	mk ('+':s)
+		| any (`elem` s) "*?" =
+			Right $ AddMatching $ compileGlob s CaseSensative
+		| otherwise = Right $ AddRef $ Ref s
+	mk ('-':s) = Right $ RemoveMatching $ compileGlob s CaseSensative
+	mk s = Left $ "bad refspec item \"" ++ s ++ "\" (expected + or - prefix)"
+
+applyRefSpec :: RefSpec -> [Ref] -> [Ref]
+applyRefSpec refspec rs = go [] refspec
+  where
+	go c [] = reverse c
+	go c (AddRef r : rest) = go (r:c) rest
+	go c (AddMatching g : rest) =
+		let add = filter (matchGlob g . fromRef) rs
+		in go (add ++ c) rest
+	go c (RemoveMatching g : rest) = 
+		go (filter (not . matchGlob g . fromRef) c) rest