add standard group selector to repo edit form

Types/StandardGroups.hs

@@ -0,0 +1,37 @@
+{- git-annex standard repository groups
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Types.StandardGroups where
+
+data StandardGroup = ClientGroup | TransferGroup | ArchiveGroup | BackupGroup
+	deriving (Eq, Ord, Enum, Bounded, Show)
+
+fromStandardGroup :: StandardGroup -> String
+fromStandardGroup ClientGroup = "client"
+fromStandardGroup TransferGroup = "transfer"
+fromStandardGroup ArchiveGroup = "archive"
+fromStandardGroup BackupGroup = "backup"
+
+toStandardGroup :: String -> Maybe StandardGroup
+toStandardGroup "client" = Just ClientGroup
+toStandardGroup "transfer" = Just TransferGroup
+toStandardGroup "archive" = Just ArchiveGroup
+toStandardGroup "backup" = Just BackupGroup
+toStandardGroup _ = Nothing
+
+descStandardGroup :: StandardGroup -> String
+descStandardGroup ClientGroup = "client: a repository on your computer"
+descStandardGroup TransferGroup = "transfer: distributes data to clients"
+descStandardGroup ArchiveGroup = "archive: collect content that is not archived elsewhere"
+descStandardGroup BackupGroup = "backup: collects all content"
+
+{- See doc/preferred_content.mdwn for explanations of these expressions. -}
+preferredContent :: StandardGroup -> String
+preferredContent ClientGroup = "exclude=*/archive/*"
+preferredContent TransferGroup = "not inallgroup=client and " ++ preferredContent ClientGroup
+preferredContent ArchiveGroup = "not copies=archive:1"
+preferredContent BackupGroup = "" -- all content is preferred