This PR will be enable editing multi files with same name.

In the case below, first file was overwritten by another file.

1. start editing my-file.txt in first console

   $ s3-edit edit s3://my-bucket/my-file.txt

2. open another console and start editing my-file.txt on another bucket (or directory).

   $ s3-edit edit s3://other-bucket/my-file.txt
   if using vim, it displays attention here.

3. end editing first console without saving.
   • if end editing with saving, it displays warning.
4. s3://my-bucket/my-file.txt was overwritten by s3://other-bucket/my-file.txt