localrepo: add git extension to autoextensions list

Differential Revision: https://phab.mercurial-scm.org/D8266

mercurial/localrepo.py

@@ -699,6 +699,7 b' def afterhgrcload(ui, wdirvfs, hgvfs, re'
     # Map of requirements to list of extensions to load automatically when
     # requirement is present.
     autoextensions = {
+        b'git': [b'git'],
         b'largefiles': [b'largefiles'],
         b'lfs': [b'lfs'],
     }