more command-specific options

Made --from and --to command-specific options.

Added generic storage for values of command-specific options,
which allows removing some of the special case fields in AnnexState.

(Also added generic storage for command-specific flags, although there are
not yet any.)

Note that this storage uses a Map, so repeatedly looking up the same value
is slightly more expensive than looking up an AnnexState field. But, the
value can be looked up once in the seek stage, transformed as necessary,
and passed in a closure to the start stage, and this avoids that overhead.

Still, I'm hesitant to use this for things like force or fast flags.
It's probably best to reserve it for flags that are only used by a few
commands, or options like --from and --to that it's important only be
allowed to be used with commands that implement them, to avoid user
confusion.

Annex.hs

@@ -17,6 +17,10 @@ module Annex (
 	eval,
 	getState,
 	changeState,
+	setFlag,
+	setField,
+	getFlag,
+	getField,
 	gitRepo,
 	inRepo,
 	fromRepo,
@@ -38,7 +42,6 @@ import Types.BranchState
 import Types.TrustLevel
 import Types.UUID
 import qualified Utility.Matcher
-import qualified Utility.Format
 import qualified Data.Map as M
 
 -- git-annex's monad
@@ -76,17 +79,16 @@ data AnnexState = AnnexState
 	, force :: Bool
 	, fast :: Bool
 	, auto :: Bool
-	, format :: Maybe Utility.Format.Format
 	, branchstate :: BranchState
 	, catfilehandle :: Maybe CatFileHandle
 	, forcebackend :: Maybe String
 	, forcenumcopies :: Maybe Int
-	, toremote :: Maybe String
-	, fromremote :: Maybe String
 	, limit :: Matcher (FilePath -> Annex Bool)
 	, forcetrust :: [(UUID, TrustLevel)]
 	, trustmap :: Maybe TrustMap
 	, ciphers :: M.Map EncryptedCipher Cipher
+	, flags :: M.Map String Bool
+	, fields :: M.Map String String
 	}
 
 newState :: Git.Repo -> AnnexState
@@ -99,17 +101,16 @@ newState gitrepo = AnnexState
 	, force = False
 	, fast = False
 	, auto = False
-	, format = Nothing
 	, branchstate = startBranchState
 	, catfilehandle = Nothing
 	, forcebackend = Nothing
 	, forcenumcopies = Nothing
-	, toremote = Nothing
-	, fromremote = Nothing
 	, limit = Left []
 	, forcetrust = []
 	, trustmap = Nothing
 	, ciphers = M.empty
+	, flags = M.empty
+	, fields = M.empty
 	}
 
 {- Create and returns an Annex state object for the specified git repo. -}
@@ -134,6 +135,24 @@ getState = gets
 changeState :: (AnnexState -> AnnexState) -> Annex ()
 changeState = modify
 
+{- Sets a flag to True -}
+setFlag :: String -> Annex ()
+setFlag flag = changeState $ \s ->
+	s { flags = M.insert flag True $ flags s }
+
+{- Sets a field to a value -}
+setField :: String -> String -> Annex ()
+setField field value = changeState $ \s ->
+	s { fields = M.insert field value $ fields s }
+
+{- Checks if a flag was set. -}
+getFlag :: String -> Annex Bool
+getFlag flag = fromMaybe False . M.lookup flag <$> getState flags
+
+{- Gets the value of a field. -}
+getField :: String -> Annex (Maybe String)
+getField field = M.lookup field <$> getState fields
+
 {- Returns the annex's git repository. -}
 gitRepo :: Annex Git.Repo
 gitRepo = getState repo