let optparse-applicative handle the usage display when run w/o command or bad command

Still generating the list of commands myself, to get it sorted into
sections and with short synopses.

CmdLine.hs

@@ -14,6 +14,7 @@ module CmdLine (
 ) where
 
 import qualified Options.Applicative as O
+import qualified Options.Applicative.Help as H
 import qualified Control.Exception as E
 import qualified Data.Map as M
 import Control.Exception (throw)
@@ -32,8 +33,8 @@ import Command
 import Types.Messages
 
 {- Runs the passed command line. -}
-dispatch :: Bool -> CmdParams -> [Command] -> [Option] -> [(String, String)] -> String -> IO Git.Repo -> IO ()
-dispatch fuzzyok allargs allcmds commonoptions fields header getgitrepo = do
+dispatch :: Bool -> CmdParams -> [Command] -> [Option] -> [(String, String)] -> IO Git.Repo -> String -> String -> IO ()
+dispatch fuzzyok allargs allcmds commonoptions fields getgitrepo progname progdesc = do
 	setupConsole
 	go =<< (E.try getgitrepo :: IO (Either E.SomeException Git.Repo))
   where
@@ -59,46 +60,52 @@ dispatch fuzzyok allargs allcmds commonoptions fields header getgitrepo = do
 		a
 
 	parsewith getparser ingitrepo = 
-		case parseCmd allargs allcmds getparser of
+		case parseCmd progname progdesc allargs allcmds getparser of
 			O.Failure _ -> do
 				-- parse failed, so fall back to
 				-- fuzzy matching, or to showing usage
 				when fuzzy $
 					ingitrepo autocorrect
-				liftIO (O.handleParseResult (parseCmd (name:args) allcmds getparser))
+				liftIO (O.handleParseResult (parseCmd progname progdesc correctedargs allcmds getparser))
 			res -> liftIO (O.handleParseResult res)
 	  where
-		autocorrect = Git.AutoCorrect.prepare inputcmdname cmdname cmds
-		err msg = msg ++ "\n\n" ++ usage header allcmds
-		(fuzzy, cmds, inputcmdname, args) = findCmd fuzzyok allargs allcmds err
+		autocorrect = Git.AutoCorrect.prepare (fromJust inputcmdname) cmdname cmds
+		(fuzzy, cmds, inputcmdname, args) = findCmd fuzzyok allargs allcmds
 		name
 			| fuzzy = case cmds of
-				(c:_) -> cmdname c
+				(c:_) -> Just (cmdname c)
 				_ -> inputcmdname
 			| otherwise = inputcmdname
+		correctedargs = case name of
+			Nothing -> allargs
+			Just n -> n:args
 
 {- Parses command line, selecting one of the commands from the list. -}
-parseCmd :: CmdParams -> [Command] -> (Command -> O.Parser v) -> O.ParserResult (Command, v)
-parseCmd allargs allcmds getparser = O.execParserPure (O.prefs O.idm) pinfo allargs
+parseCmd :: String -> String -> CmdParams -> [Command] -> (Command -> O.Parser v) -> O.ParserResult (Command, v)
+parseCmd progname progdesc allargs allcmds getparser = O.execParserPure (O.prefs O.idm) pinfo allargs
   where
-	pinfo = O.info (O.helper <*> subcmds) O.fullDesc
+	pinfo = O.info (O.helper <*> subcmds) (O.progDescDoc (Just intro))
 	subcmds = O.hsubparser $ mconcat $ map mkcommand allcmds
-	mkcommand c = O.command (cmdname c) $ O.info (mkparser c) 
-		(O.fullDesc <> O.header (cmddesc c) <> O.progDesc (cmddesc c))
+	mkcommand c = O.command (cmdname c) $ O.info (mkparser c) $ O.fullDesc 
+		<> O.header (synopsis (progname ++ " " ++ cmdname c) (cmddesc c))
+		<> O.footer ("For details, run: " ++ progname ++ " help " ++ cmdname c)
 	mkparser c = (,)
 		<$> pure c
 		<*> getparser c
+	synopsis n d = n ++ " - " ++ d
+	intro = mconcat $ concatMap (\l -> [H.text l, H.line])
+		(synopsis progname progdesc : commandList allcmds)
 
 {- Parses command line params far enough to find the Command to run, and
  - returns the remaining params.
  - Does fuzzy matching if necessary, which may result in multiple Commands. -}
-findCmd :: Bool -> CmdParams -> [Command] -> (String -> String) -> (Bool, [Command], String, CmdParams)
-findCmd fuzzyok argv cmds err
-	| isNothing name = error $ err "missing command"
-	| not (null exactcmds) = (False, exactcmds, fromJust name, args)
-	| fuzzyok && not (null inexactcmds) = (True, inexactcmds, fromJust name, args)
-	| otherwise = error $ err $ "unknown command " ++ fromJust name
+findCmd :: Bool -> CmdParams -> [Command] -> (Bool, [Command], Maybe String, CmdParams)
+findCmd fuzzyok argv cmds
+	| not (null exactcmds) = ret (False, exactcmds)
+	| fuzzyok && not (null inexactcmds) = ret (True, inexactcmds)
+	| otherwise = ret (False, [])
   where
+	ret (fuzzy, matches) = (fuzzy, matches, name, args)
 	(name, args) = findname argv []
 	findname [] c = (Nothing, reverse c)
 	findname (a:as) c

CmdLine/GitAnnex.hs

@@ -19,6 +19,7 @@ import qualified Command.Add
 import qualified Command.Unannex
 import qualified Command.Fsck
 {-
+import qualified Command.Help
 import qualified Command.Drop
 import qualified Command.Move
 import qualified Command.Copy
@@ -97,7 +98,6 @@ import qualified Command.Proxy
 import qualified Command.DiffDriver
 import qualified Command.Undo
 import qualified Command.Version
-import qualified Command.Help
 #ifdef WITH_ASSISTANT
 import qualified Command.Watch
 import qualified Command.Assistant
@@ -124,6 +124,7 @@ cmds =
 	[ Command.Add.cmd
 	, Command.Fsck.cmd
 {-
+	, Command.Help.cmd
 	, Command.Get.cmd
 	, Command.Drop.cmd
 	, Command.Move.cmd
@@ -204,7 +205,6 @@ cmds =
 	, Command.DiffDriver.cmd
 	, Command.Undo.cmd
 	, Command.Version.cmd
-	, Command.Help.cmd
 #ifdef WITH_ASSISTANT
 	, Command.Watch.cmd
 	, Command.Assistant.cmd
@@ -224,9 +224,6 @@ cmds =
 -}
 	]
 
-header :: String
-header = "git-annex command [option ...]"
-
 run :: [String] -> IO ()
 run args = do
 #ifdef WITH_EKG
@@ -234,7 +231,9 @@ run args = do
 #endif
 	go envmodes
   where
-	go [] = dispatch True args cmds gitAnnexOptions [] header Git.CurrentRepo.get
+	go [] = dispatch True args cmds gitAnnexOptions [] Git.CurrentRepo.get
+		"git-annex"
+		"manage files with git, without checking their contents in"
 	go ((v, a):rest) = maybe (go rest) a =<< getEnv v
 	envmodes =
 		[ (sshOptionsEnv, runSshOptions args)

CmdLine/GitAnnexShell.hs

@@ -101,7 +101,9 @@ builtin cmd dir params = do
 	let (params', fieldparams, opts) = partitionParams params
 	    rsyncopts = ("RsyncOptions", unwords opts)
 	    fields = rsyncopts : filter checkField (parseFields fieldparams)
-	dispatch False (cmd : params') cmds options fields header mkrepo
+	dispatch False (cmd : params') cmds options fields mkrepo
+		"git-annex-shell"
+		"Restricted login shell for git-annex only SSH access"
   where
 	mkrepo = do
 		r <- Git.Construct.repoAbsPath dir >>= Git.Construct.fromAbsPath

CmdLine/Usage.hs

@@ -13,9 +13,12 @@ import Types.Command
 usageMessage :: String -> String
 usageMessage s = "Usage: " ++ s
 
-{- Usage message with lists of commands by section. -}
 usage :: String -> [Command] -> String
-usage header cmds = unlines $ usageMessage header : concatMap go [minBound..]
+usage header cmds = unlines $ usageMessage header : commandList cmds
+
+{- Commands listed by section, with breif usage and description. -}
+commandList :: [Command] -> [String]
+commandList cmds = concatMap go [minBound..]
   where
 	go section
 		| null cs = []
@@ -39,6 +42,7 @@ usage header cmds = unlines $ usageMessage header : concatMap go [minBound..]
 	longest f = foldl max 0 $ map (length . f) cmds
 	scmds = sort cmds
 
+
 {- Descriptions of params used in usage messages. -}
 paramPaths :: String
 paramPaths = paramRepeating paramPath -- most often used

Command/Help.hs

@@ -56,8 +56,8 @@ showGeneralHelp = putStrLn $ unlines
 		, Command.Whereis.cmd
 		, Command.Fsck.cmd
 		]
-	, "Run 'git-annex' for a complete command list."
-	, "Run 'git-annex help command' for help on a specific command."
+	, "For a complete command list, run: git-annex"
+	, "For help on a specific command, run: git-annex help COMMAND"
 	]
   where
 	cmdline c = "\t" ++ cmdname c ++ "\t" ++ cmddesc c