$ git clone -n https://src.fedoraproject.org/rpms/gstreamer1-plugins-base.git /var/lib/mock/f42-build-side-1-3584713-46895/root/chroot_tmpdir/scmroot/gstreamer1-plugins-base
Cloning into '/var/lib/mock/f42-build-side-1-3584713-46895/root/chroot_tmpdir/scmroot/gstreamer1-plugins-base'...
$ git fetch origin acb536b9644dfbc0ba93f96b7064d44b9bb52a42:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gstreamer1-plugins-base
 * [new ref]         acb536b9644dfbc0ba93f96b7064d44b9bb52a42 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at acb536b 1.26.3