Improve the "Try making some of these repositories available" message

With some hints for the user for what to do.

Took care to avoid changing the json output. It would have been ok to add
the new separated lists to it, in addition to the old list, but I didn't
do that because I didn't see much point.

Remote.hs

@@ -1,6 +1,6 @@
 {- git-annex remotes
  -
- - Copyright 2011-2019 Joey Hess <id@joeyh.name>
+ - Copyright 2011-2020 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -73,6 +73,7 @@ import Annex.UUID
 import Logs.UUID
 import Logs.Trust
 import Logs.Location hiding (logStatus)
+import Logs.Remote
 import Logs.Web
 import Remote.List
 import Remote.List.Util
@@ -337,31 +338,53 @@ remoteLocations locations trusted = do
 
 	return (sortBy (comparing cost) validremotes, validtrustedlocations)
 
-{- Displays known locations of a key. -}
+{- Displays known locations of a key and helps the user take action
+ - to make them accessible. -}
 showLocations :: Bool -> Key -> [UUID] -> String -> Annex ()
 showLocations separateuntrusted key exclude nolocmsg = do
 	u <- getUUID
+	remotes <- remoteList
 	uuids <- keyLocations key
 	untrusteduuids <- if separateuntrusted
 		then trustGet UnTrusted
 		else pure []
-	let uuidswanted = filteruuids uuids (u:exclude++untrusteduuids) 
+	let uuidswanted = filteruuids uuids (u:exclude++untrusteduuids)
 	let uuidsskipped = filteruuids uuids (u:exclude++uuidswanted)
-	ppuuidswanted <- prettyPrintUUIDs "wanted" uuidswanted
-	ppuuidsskipped <- prettyPrintUUIDs "skipped" uuidsskipped
-	let msg = message ppuuidswanted ppuuidsskipped
-	unless (null msg) $
-		showLongNote msg
-	ignored <- remoteList
-		>>= filterM (liftIO . getDynamicConfig . remoteAnnexIgnore . gitconfig)
+	let remoteuuids = map uuid remotes
+	let isremoteuuid x = elem x remoteuuids
+	let (remotesmakeavailable, uuidsothers) = 
+		partition isremoteuuid uuidswanted
+	isspecialremote <- flip M.member <$> remoteConfigMap
+	let (enablespecialremotes, addgitremotes) = 
+		partition isspecialremote uuidsothers
+	
+	-- Add "wanted" field to the JSON. While it's since been split
+	-- up more, this avoids breaking any JSON parsers that expect it.
+	ifM jsonOutputEnabled
+		( void $ prettyPrintUUIDs "wanted" uuidswanted
+		, do
+			ppremotesmakeavailable <- pp "remotes" remotesmakeavailable
+				"Try making some of these remotes available"
+			ppenablespecialremotes <- pp "enableremote" enablespecialremotes
+				"Maybe enable some of these special remotes (git annex initremote ...)"
+			ppaddgitremotes <- pp "repos" addgitremotes
+				"Maybe add some of these git remotes (git remote add ...)"
+			ppuuidsskipped <- pp "skipped" uuidsskipped
+				"Also these untrusted repositories may contain the file"
+			showLongNote $ case ppremotesmakeavailable ++ ppenablespecialremotes ++ ppaddgitremotes ++ ppuuidsskipped of
+				[] -> nolocmsg
+				s -> s
+		)
+	ignored <- filterM (liftIO . getDynamicConfig . remoteAnnexIgnore . gitconfig) remotes
 	unless (null ignored) $
 		showLongNote $ "(Note that these git remotes have annex-ignore set: " ++ unwords (map name ignored) ++ ")"
   where
 	filteruuids l x = filter (`notElem` x) l
-	message [] [] = nolocmsg
-	message rs [] = "Try making some of these repositories available:\n" ++ rs
-	message [] us = "Also these untrusted repositories may contain the file:\n" ++ us
-	message rs us = message rs [] ++ message [] us
+
+	pp jh l h = addheader h <$> prettyPrintUUIDs jh l
+
+	addheader _ [] = []
+	addheader h l = h ++ ":\n" ++ l
 
 showTriedRemotes :: [Remote] -> Annex ()
 showTriedRemotes [] = noop