tarfile forgets set sgid when targetpath has it

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-09-26.14:12:19.762>
labels = ['3.7', 'type-bug', 'library']
title = 'tarfile forgets set sgid when targetpath has it'
updated_at = <Date 2019-10-25.13:52:47.303>
user = 'https://bugs.python.org/CharlesCoulombe'

bugs.python.org fields:

activity = <Date 2019-10-25.13:52:47.303>
actor = 'Charles Coulombe'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-09-26.14:12:19.762>
creator = 'Charles Coulombe'
dependencies = []
files = ['48678']
hgrepos = []
issue_num = 38286
keywords = ['patch']
message_count = 1.0
messages = ['353305']
nosy_count = 1.0
nosy_names = ['Charles Coulombe']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue38286'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6', 'Python 3.7']