BUG #11949: pg_basebackup creates defective tar file

The following bug has been logged on the website:

Bug reference:      11949
Logged by:          Hendrik Grewe
Email address:      hendrik.grewe@udo.edu
PostgreSQL version: 9.3.5
Operating system:   Ubuntu Linux 12.04 / Kernel 3.13.0-39
Description:

Hi!
Somehow pg_basebackup constructs defective tar files if invoked like

pg_basebackup --pgdata=/path/to/folder --format=tar --label="pg_backup on
2012.10.21"

The resulting base.tar in path/to/folder is somwhat corrupted.
It is possible to untar this file but it is somehow impossible to add a file
to the generate base.tar file throug

tar --append --file /path/to/folder/base.tar someFileToAddToArchive

This is also an error within TAR, because it silently (Exit Code 0) fails to
add the File `someFileToAddToArchive`. But this faulty try to add the file
results in a changed/repaired base.tar. If one trys to append the file on
this tampered tar it will work and the file is actually added to the tar.

Bugreport to TAR project is on its way, also.
Since other "handmade" tars do work on appending files, the generated
base.tar file by pg_basebackup must be somhow broken.

If You need additional informations feel free to contact me.