$ git clone -n https://src.fedoraproject.org/rpms/perl-Sys-Mmap.git /var/lib/mock/f45-build-26364-617/root/chroot_tmpdir/scmroot/perl-Sys-Mmap
Cloning into '/var/lib/mock/f45-build-26364-617/root/chroot_tmpdir/scmroot/perl-Sys-Mmap'...
$ git fetch origin 977acf98847a2513a5ceee16c68930af8123980d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Sys-Mmap
 * [new ref]         977acf98847a2513a5ceee16c68930af8123980d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 977acf9 Perl 5.44 rebuild