Merge branch 'cl/rerere-train-with-no-sign' into maint

"rerere-train" script (in contrib/) used to honor commit.gpgSign
while recreating the throw-away merges.
source: <PH7PR14MB5594A27B9295E95ACA4D6A69CE8F9@PH7PR14MB5594.namprd14.prod.outlook.com>

* cl/rerere-train-with-no-sign:
  contrib/rerere-train: avoid useless gpg sign in training