stop warning about removals from IA

In a test, I uploaded a pdf, and several files were derived from it.
After removing the pdf, the derived files went away after approximatly
half an hour. This window does not seem worth warning about every time.
Documented it in the tip.

CHANGELOG

@@ -9,8 +9,7 @@ git-annex (6.20170819) UNRELEASED; urgency=medium
   * Support building with feed-1.0, while still supporting older versions.
   * init: Display an additional message when it detects a filesystem that
     allows writing to files whose write bit is not set.
-  * S3: Allow removing files from IA, but warn about derived versions
+  * S3: Allow removing files from IA.
-    potentially still existing there.
 
  -- Joey Hess <id@joeyh.name>  Mon, 28 Aug 2017 12:20:59 -0400
 

Remote/S3.hs

@@ -278,18 +278,11 @@ retrieveCheap _ _ _ = return False
  - While it may remove the file, there are generally other files
  - derived from it that it does not remove. -}
 remove :: S3Info -> S3Handle -> Remover
-remove info h k = warnIARemoval info $ do
+remove info h k = do
 	res <- tryNonAsync $ sendS3Handle h $
 		S3.DeleteObject (T.pack $ bucketObject info k) (bucket info)
 	return $ either (const False) (const True) res
 
-warnIARemoval :: S3Info -> Annex a -> Annex a
-warnIARemoval info a
-	| isIA info = do
-		warning "Derived versions of removed file may still be present in the Internet Archive"
-		a
-	| otherwise = a
-
 checkKey :: Remote -> S3Info -> Maybe S3Handle -> CheckPresent
 checkKey r info Nothing k = case getpublicurl info of
 	Nothing -> do
@@ -345,7 +338,7 @@ retrieveExportS3 r info _k loc f p =
 		return True
 
 removeExportS3 :: Remote -> S3Info -> Key -> ExportLocation -> Annex Bool
-removeExportS3 r info _k loc = warnIARemoval info $
+removeExportS3 r info _k loc = 
 	catchNonAsync go (\e -> warning (show e) >> return False)
   where
 	go = withS3Handle (config r) (gitconfig r) (uuid r) $ \h -> do

doc/tips/Internet_Archive_via_S3.mdwn

@@ -51,15 +51,15 @@ Then you can annex files and copy them to the remote as usual:
 	# git annex copy photo1.jpeg --fast --to archive-panama
 	copy (to archive-panama...) ok
 
+## update lag
+
 It may take a while for archive.org to make files publically visible after
 they've been uploaded.
 
-## removing files
-
 While files can be removed from the Internet Archive, 
 [derived versions](https://archive.org/help/derivatives.php)
-of some files may continued to be stored there after the originals
+of some files may continued to be stored there for a while
-were removed. git-annex warns about this problem.
+after the originals were removed.
 
 ## exporting trees