$ git clone -n https://src.fedoraproject.org/rpms/gdb.git /var/lib/mock/f42-build-3156422-40813/root/chroot_tmpdir/scmroot/gdb
Cloning into '/var/lib/mock/f42-build-3156422-40813/root/chroot_tmpdir/scmroot/gdb'...
$ git fetch origin 757a596c588ab59706d8f4796ce09b538dd9e562:KOJI_FETCH_HEAD
error: Server does not allow request for unadvertised object 757a596c588ab59706d8f4796ce09b538dd9e562
$ git reset --hard 757a596c588ab59706d8f4796ce09b538dd9e562
fatal: Could not parse object '757a596c588ab59706d8f4796ce09b538dd9e562'.