Merge pull request #4179 from filecoin-project/fix/export-unclean-exit

chain export: Error with unfinished exports

cli/chain.go

@@ -1070,13 +1070,20 @@ var chainExportCmd = &cli.Command{
 			return err
 		}
 
+		var last bool
 		for b := range stream {
+			last = len(b) == 0
+
 			_, err := fi.Write(b)
 			if err != nil {
 				return err
 			}
 		}
 
+		if !last {
+			return xerrors.Errorf("incomplete export (remote connection lost?)")
+		}
+
 		return nil
 	},
 }