add GETAVAILABILITY to external special remote protocol

And some reworking of types, and added an annex-availability git config
setting.

Remote/Helper/Git.hs

@@ -1,6 +1,6 @@
 {- Utilities for git remotes.
  -
- - Copyright 2011-2012 Joey Hess <joey@kitenet.net>
+ - Copyright 2011-2014 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -9,18 +9,20 @@ module Remote.Helper.Git where
 
 import Common.Annex
 import qualified Git
+import Types.Availability
 
 repoCheap :: Git.Repo -> Bool
 repoCheap = not . Git.repoIsUrl
 
 localpathCalc :: Git.Repo -> Maybe FilePath
-localpathCalc r = if globallyAvailableCalc r
-	then Nothing
-	else Just $ Git.repoPath r
+localpathCalc r
+	| availabilityCalc r == GloballyAvailable = Nothing
+	| otherwise = Just $ Git.repoPath r
 
-globallyAvailableCalc :: Git.Repo -> Bool
-globallyAvailableCalc r = not $
-	Git.repoIsLocal r || Git.repoIsLocalUnknown r
+availabilityCalc :: Git.Repo -> Availability
+availabilityCalc r
+	| (Git.repoIsLocal r || Git.repoIsLocalUnknown r) = LocallyAvailable
+	| otherwise = GloballyAvailable
 
 {- Avoids performing an action on a local repository that's not usable.
  - Does not check that the repository is still available on disk. -}