migrate: Don't fall over a stale temp file.

Command/Migrate.hs

@@ -48,9 +48,10 @@ perform file oldkey newbackend = do
 	src <- fromRepo $ gitAnnexLocation oldkey
 	tmp <- fromRepo gitAnnexTmpDir
 	let tmpfile = tmp </> takeFileName file
+	cleantmp tmpfile
 	liftIO $ createLink src tmpfile
 	k <- Backend.genKey tmpfile $ Just newbackend
-	liftIO $ cleantmp tmpfile
+	cleantmp tmpfile
 	case k of
 		Nothing -> stop
 		Just (newkey, _) -> do
@@ -70,7 +71,7 @@ perform file oldkey newbackend = do
 					next $ Command.Add.cleanup file newkey True
 				else stop
 	where
-		cleantmp t = whenM (doesFileExist t) $ removeFile t
+		cleantmp t = liftIO $ whenM (doesFileExist t) $ removeFile t
 		link src newkey = getViaTmpUnchecked newkey $ \t -> do
 			-- Make a hard link to the old backend's
 			-- cached key, to avoid wasting disk space.

debian/changelog

@@ -16,6 +16,7 @@ git-annex (3.20111112) UNRELEASED; urgency=low
   * Fix support for insteadOf url remapping. Closes: #644278
   * When not run in a git repository, git-annex can still display a usage
     message, and "git annex version" even works.
+  * migrate: Don't fall over a stale temp file.
 
  -- Joey Hess <joeyh@debian.org>  Sat, 12 Nov 2011 14:50:21 -0400
 

doc/bugs/interrupting_migration_causes_problems.mdwn

@@ -47,4 +47,6 @@ The error:
     failed
     git-annex: migrate: 1 failed
 
-    
+> Fixed it to delete the stale temp file. [[done]]
+> 
+> Thanks for making such clear test cases, Jim! --[[Joey]]