Fix how version_info omits non-numeric fields

For gitpython-developers#1833.

This makes version_info parsing stop including fields after the
first non-numeric field, rather than skipping non-numeric fields
and including subsequent numeric fields that then wrongly appear to
have the original position and significance of the dropped field.

This actually stops at (rather than merely after) a non-numeric
field, i.e., potentially parseable fields that are not fully
numeric, such as "2a", are stopped at, rather than parsed as "2".

git/cmd.py

@@ -8,6 +8,7 @@
 import re
 import contextlib
 import io
+import itertools
 import logging
 import os
 import signal
@@ -850,7 +851,8 @@ def version_info(self) -> Tuple[int, ...]:
         process_version = self._call_process("version")
         version_string = process_version.split(" ")[2]
         version_fields = version_string.split(".")[:4]
-        self._version_info = tuple(int(n) for n in version_fields if n.isdigit())
+        leading_numeric_fields = itertools.takewhile(str.isdigit, version_fields)
+        self._version_info = tuple(map(int, leading_numeric_fields))
 
         # This value will be considered valid until the next refresh.
         self._version_info_token = refresh_token