init: Detect when the filesystem is crippled such that it ignores attempts to remove the write bit from a file, and enable direct mode. Seen with eg, NTFS fuse on linux.

Annex/Init.hs

@@ -128,6 +128,7 @@ probeCrippledFileSystem = do
 	createAnnexDirectory tmp
 	liftIO $ writeFile f ""
 	uncrippled <- liftIO $ probe f
+	void $ liftIO $ tryIO $ allowWrite f
 	liftIO $ removeFile f
 	return $ not uncrippled
   where
@@ -137,8 +138,9 @@ probeCrippledFileSystem = do
 		createSymbolicLink f f2
 		nukeFile f2
 		preventWrite f
-		allowWrite f
+		-- Should be unable to write to the file, but some crippled
-		return True
+		-- filesystems ignore write bit removals.
+		not <$> catchBoolIO (writeFile f "2" >> return True)
 #endif
 
 checkCrippledFileSystem :: Annex ()

debian/changelog

@@ -6,6 +6,9 @@ git-annex (5.20150728) UNRELEASED; urgency=medium
   * The last release accidentially removed a number of options from the
     copy command. (-J, file matching options, etc). These have been added
     back.
+  * init: Detect when the filesystem is crippled such that it ignores
+    attempts to remove the write bit from a file, and enable direct mode.
+    Seen with eg, NTFS fuse on linux.
 
  -- Joey Hess <id@joeyh.name>  Mon, 27 Jul 2015 15:57:07 -0400
 

doc/forum/git-annex_does_not_protect_files_on_NTFS-Fuse/comment_1_4aef65f680e4801eb110fefa1f947f02._comment

@@ -0,0 +1,11 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 1"""
+ date="2015-07-30T17:54:11Z"
+ content="""
+Good idea. Also, putting an indirect mode repo on a NTFS filesystem would
+probably yield confusing results when trying to use it on windows..
+
+I've put a check for this in with the other crippled FS checks that init
+does.
+"""]]