$ git clone -n https://src.fedoraproject.org/rpms/rust-is-macro.git /var/lib/mock/f45-build-42671-795/root/chroot_tmpdir/scmroot/rust-is-macro
Cloning into '/var/lib/mock/f45-build-42671-795/root/chroot_tmpdir/scmroot/rust-is-macro'...
$ git fetch origin e59c7cc2674ee847f555482c1a46de06e4cf9be8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-is-macro
 * [new ref]         e59c7cc2674ee847f555482c1a46de06e4cf9be8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e59c7cc Update to version 0.3.8; Fixes RHBZ#2521264