seek: defer matcher check until more info is known

Sped up seeking for files to operate on, when using options like --copies
or --in, by around 20%.

Benchmark showed an increase for --copies from 155 seconds to 121
seconds, and --in remote will be similar to that.

For --in here, the speedup was less, 5-10% or so.

(both warm cache)

This commit was sponsored by Jack Hill on Patreon.

Limit/Wanted.hs

@@ -1,6 +1,6 @@
 {- git-annex limits by wanted status
  -
- - Copyright 2012 Joey Hess <id@joeyh.name>
+ - Copyright 2012-2020 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -11,20 +11,27 @@ import Annex.Common
 import Annex.Wanted
 import Limit
 import Types.FileMatcher
+import Logs.PreferredContent
 
 addWantGet :: Annex ()
-addWantGet = addLimit $ Right $ MatchFiles
-	{ matchAction = const $ checkWant $ wantGet False Nothing
-	, matchNeedsFileName = False
-	, matchNeedsFileContent = False
-	}
+addWantGet = addPreferredContentLimit $
+	checkWant $ wantGet False Nothing
 
 addWantDrop :: Annex ()
-addWantDrop = addLimit $ Right $ MatchFiles
-	{ matchAction = const $ checkWant $ wantDrop False Nothing Nothing
-	, matchNeedsFileName = False
-	, matchNeedsFileContent = False
-	}
+addWantDrop = addPreferredContentLimit $
+	checkWant $ wantDrop False Nothing Nothing
+
+addPreferredContentLimit :: (MatchInfo -> Annex Bool) -> Annex ()
+addPreferredContentLimit a = do
+	nfn <- introspectPreferredRequiredContent matchNeedsFileName Nothing
+	nfc <- introspectPreferredRequiredContent matchNeedsFileContent Nothing
+	nk <- introspectPreferredRequiredContent matchNeedsKey Nothing
+	addLimit $ Right $ MatchFiles
+		{ matchAction = const a
+		, matchNeedsFileName = nfn
+		, matchNeedsFileContent = nfc
+		, matchNeedsKey = nk
+		}
 
 checkWant :: (AssociatedFile -> Annex Bool) -> MatchInfo -> Annex Bool
 checkWant a (MatchingFile fi) = a (AssociatedFile (Just $ matchFile fi))