$ git clone -n https://src.fedoraproject.org/rpms/rust-rand_isaac.git /var/lib/mock/f45-build-44251-811/root/chroot_tmpdir/scmroot/rust-rand_isaac
Cloning into '/var/lib/mock/f45-build-44251-811/root/chroot_tmpdir/scmroot/rust-rand_isaac'...
$ git fetch origin 4a7f20dada12a2f752300162fdd343598004e3cb:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-rand_isaac
 * [new ref]         4a7f20dada12a2f752300162fdd343598004e3cb -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4a7f20d Update to version 0.5.1; Fixes RHBZ#2480098