interrupted export recovery bugfixes

When an export was interrupted, the sqlite database won't have been
committed necessarily. Also, the interrupted export might have been
run in an entirely different repository. There's not a significant speed
benefit in checking getExportLocation in this case anyway, so avoid it.

Also, remove the old filename from the export database.

Recovery from interrupted exports is now tested working.

This commit was supported by the NSF-funded DataLad project.

Command/Export.hs

@@ -96,7 +96,9 @@ seek o = do
 	-- temp files. Diff from the incomplete tree to the new tree,
 	-- and delete any temp files that the new tree can't use.
 	forM_ (concatMap incompleteExportedTreeish old) $ \incomplete ->
-		mapdiff (startUnexportTempName r db . Git.DiffTree.srcsha) incomplete new
+		mapdiff (\diff -> startRecoverIncomplete r db (Git.DiffTree.srcsha diff) (Git.DiffTree.file diff))
+			incomplete
+			new
 
 	-- Diff the old and new trees, and delete or rename to new name all
 	-- changed files in the export. After this, every file that remains
@@ -264,15 +266,18 @@ cleanupUnexport r db eks loc = do
 			logChange (asKey ek) (uuid r) InfoMissing
 	return True
 
-startUnexportTempName :: Remote -> ExportHandle -> Git.Sha -> CommandStart
-startUnexportTempName r db sha
+startRecoverIncomplete :: Remote -> ExportHandle -> Git.Sha -> TopFilePath -> CommandStart
+startRecoverIncomplete r db sha oldf
 	| sha == nullSha = stop
 	| otherwise = do
 		ek <- exportKey sha
 		let loc@(ExportLocation f) = exportTempName ek
-		stopUnless (liftIO $ elem loc <$> getExportLocation db (asKey ek)) $ do
-			showStart "unexport" f
-			next $ performUnexport r db [ek] loc
+		showStart "unexport" f
+		liftIO $ removeExportLocation db (asKey ek) oldloc
+		next $ performUnexport r db [ek] loc
+  where
+	oldloc = ExportLocation $ toInternalGitPath oldf'
+	oldf' = getTopFilePath oldf
 
 startMoveToTempName :: Remote -> ExportHandle -> TopFilePath -> ExportKey -> CommandStart
 startMoveToTempName r db f ek = do