$ git clone -n https://src.fedoraproject.org/rpms/mercurial.git /var/lib/mock/f40-build-793465-138985/root/chroot_tmpdir/scmroot/mercurial
Cloning into '/var/lib/mock/f40-build-793465-138985/root/chroot_tmpdir/scmroot/mercurial'...
$ git fetch origin 0d205186ba3581b979d7124891d824578093cecc:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mercurial
 * [new ref]         0d205186ba3581b979d7124891d824578093cecc -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0d20518 mercurial 6.6.3