avoid git annex info remote buffering list of keys

This leaves git annex unused --from remote still using loggedKeysFor
and buffering more than ought to be necessary, but I can't see a way to
improve that.

CHANGELOG

@@ -23,7 +23,8 @@ git-annex (6.20180410) UNRELEASED; urgency=medium
   * Assistant: Fix installation of menus, icons, etc when run
     from within runshell.
   * import: Avoid buffering all filenames to be imported in memory.
-  * Improve memory use and speed of --all, by not buffering list of all keys.
+  * Improve memory use and speed of --all and git-annex info remote,
+    by not buffering list of all keys.
 
  -- Joey Hess <id@joeyh.name>  Mon, 09 Apr 2018 14:03:28 -0400
 

Command/Info.hs

@@ -525,7 +525,11 @@ cachedRemoteData u = do
 	case M.lookup u (repoData s) of
 		Just v -> return v
 		Nothing -> do
-			v <- foldKeys <$> lift (loggedKeysFor u)
+			let combinedata d uk = finishCheck uk >>= \case
+				Nothing -> return d
+				Just k -> return $ addKey k d
+			v <- lift $ foldM combinedata emptyKeyData
+				=<< loggedKeysFor' u
 			put s { repoData = M.insert u v (repoData s) }
 			return v
 

Logs/Location.hs

@@ -27,6 +27,7 @@ module Logs.Location (
 	finishCheck,
 	loggedKeys,
 	loggedKeysFor,
+	loggedKeysFor',
 ) where
 
 import Annex.Common
@@ -139,10 +140,15 @@ loggedKeys' check = mapMaybe (defercheck <$$> locationLogFileKey)
 		)
 
 {- Finds all keys that have location log information indicating
- - they are present for the specified repository.
+ - they are present in the specified repository.
+ -
+ - This does not stream well; use loggedKeysFor' for lazy streaming.
  -}
 loggedKeysFor :: UUID -> Annex [Key]
-loggedKeysFor u = catMaybes <$> (mapM finishCheck =<< loggedKeys' isthere)
+loggedKeysFor u = catMaybes <$> (mapM finishCheck =<< loggedKeysFor' u)
+
+loggedKeysFor' :: UUID -> Annex [Unchecked Key]
+loggedKeysFor' u = loggedKeys' isthere
   where
 	isthere k = do
 		us <- loggedLocations k