$ git clone -n https://src.fedoraproject.org/rpms/ghc-regex-base.git /var/lib/mock/f39-build-1507217-35229/root/chroot_tmpdir/scmroot/ghc-regex-base
Cloning into '/var/lib/mock/f39-build-1507217-35229/root/chroot_tmpdir/scmroot/ghc-regex-base'...
$ git fetch origin c3797655b99dc212b6f9403ae89f17fad7c2024a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-regex-base
 * [new ref]         c3797655b99dc212b6f9403ae89f17fad7c2024a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c379765 revised .cabal file