The implementations of ISystemIO.FileOpenWrite call File.OpenWrite,
which does not truncate the existing file. As such, if we overwrite a
larger file with a smaller one, tail remnants of the existing file will
remain.
Since most of the put operations involve unique filenames, this is only
a problem when overwriting existing files (e.g.,
duplicati-verification.json).
This fixes a regression introduced in revision 71c6aca8a7 ("Fixed IO
calls in Filebackend") from pull request #3456. The previous
implementation called File.Open with FileMode.Create, which truncates
existing files.
This fixes#4486.
Kenneth Hsu
c14ace0d68