S3: Allow removing files from IA, but warn about derived versions potentially still existing there.

Removal works, only derives are a potential issue, so allow removing
with a warning. This way, unexporting a file works, and behavior is
consistent with IA remotes whether or not exporttree=yes.

Also tested exporting filenames containing unicode, spaces, underscores.
All worked, despite the IA's faq saying it doesn't.

This commit was sponsored by Trenton Cronholm on Patreon.

CHANGELOG

@@ -9,6 +9,8 @@ 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
+    potentially still existing there.
 
  -- Joey Hess <id@joeyh.name>  Mon, 28 Aug 2017 12:20:59 -0400
 

Remote/S3.hs

@@ -278,14 +278,17 @@ 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
+remove info h k = warnIARemoval info $ 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 "Cannot remove content from the Internet Archive"
-		return False
-	| otherwise = do
-		res <- tryNonAsync $ sendS3Handle h $
-			S3.DeleteObject (T.pack $ bucketObject info k) (bucket info)
-		return $ either (const False) (const True) res
+		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
@@ -342,7 +345,7 @@ retrieveExportS3 r info _k loc f p =
 		return True
 
 removeExportS3 :: Remote -> S3Info -> Key -> ExportLocation -> Annex Bool
-removeExportS3 r info _k loc = 
+removeExportS3 r info _k loc = warnIARemoval info $
 	catchNonAsync go (\e -> warning (show e) >> return False)
   where
 	go = withS3Handle (config r) (gitconfig r) (uuid r) $ \h -> do
@@ -620,9 +623,9 @@ getBucketObject c = munge . key2file
 getBucketExportLocation :: RemoteConfig -> ExportLocation -> FilePath
 getBucketExportLocation c (ExportLocation loc) = getFilePrefix c ++ loc
 
-{- Internet Archive limits filenames to a subset of ascii,
- - with no whitespace. Other characters are xml entity
- - encoded. -}
+{- Internet Archive documentation limits filenames to a subset of ascii.
+ - While other characters seem to work now, this entity encodes everything
+ - else to avoid problems. -}
 iaMunge :: String -> String
 iaMunge = (>>= munge)
   where

doc/tips/Internet_Archive_via_S3.mdwn

@@ -11,9 +11,10 @@ comply with their [terms of service](http://www.archive.org/about/terms.php).
 A nice added feature is that whenever git-annex sends a file to the
 Internet Archive, it records its url, the same as if you'd run `git annex
 addurl`. So any users who can clone your repository can download the files
-from archive.org, without needing any login or password info. This makes
-the Internet Archive a nice way to publish the large files associated with
-a public git repository.
+from archive.org, without needing any login or password info. 
+The url to the content in the Internet Archive is also displayed by
+`git annex whereis`. This makes the Internet Archive a nice way to
+publish the large files associated with a public git repository.
 
 ## webapp setup
 
@@ -50,10 +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
 
-Once a file has been stored on archive.org, it cannot be (easily) removed
-from it. Also, git-annex whereis will tell you a public url for the file
-on archive.org. (It may take a while for archive.org to make the file
-publically visibile.)
+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
+were removed. git-annex warns about this problem.
 
 ## exporting trees
 
@@ -63,6 +69,7 @@ are important, you can run `git annex initremote` with an additional
 parameter "exporttree=yes", and then use [[git-annex-export]] to publish
 a tree of files to the Internet Archive.
 
-Note that the Internet Archive does not support filenames containing
-whitespace and some other characters. Exporting such problem filenames will
-fail; you can rename the file and re-export.
+Note that the Internet Archive may not support certian characters
+in filenames ([see FAQ](http://archive.org/about/faqs.php#1099)).
+If exporting a filename fails due to such limitations, you would need
+to rename it in your git annex repository in order to export it.

doc/todo/export.mdwn

@@ -29,8 +29,6 @@ Work is in progress. Todo list:
   Would need git-annex sync to export to the master tree?
   This is similar to the little-used preferreddir= preferred content
   setting and the "public" repository group.
-* Test export to IA via S3. In particualar, does removing an exported file
-  work?
 
 Low priority: