'dirty' added to sys.version on Linux and Mac source builds depending on git version

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-06-15.10:27:55.893>
labels = ['type-feature', '3.7', 'build']
title = "'dirty' added to sys.version on Linux and Mac source builds depending on git version"
updated_at = <Date 2021-06-16.01:01:50.105>
user = 'https://bugs.python.org/markfinal'

bugs.python.org fields:

activity = <Date 2021-06-16.01:01:50.105>
actor = 'ned.deily'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Build']
creation = <Date 2021-06-15.10:27:55.893>
creator = 'mark.final'
dependencies = []
files = []
hgrepos = []
issue_num = 44425
keywords = []
message_count = 1.0
messages = ['395866']
nosy_count = 2.0
nosy_names = ['ned.deily', 'mark.final']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue44425'
versions = ['Python 3.7']