$ git clone -n https://src.fedoraproject.org/rpms/rust-url.git /var/lib/mock/f42-build-side-1-3500262-45970/root/chroot_tmpdir/scmroot/rust-url
Cloning into '/var/lib/mock/f42-build-side-1-3500262-45970/root/chroot_tmpdir/scmroot/rust-url'...
$ git fetch origin 38b9eea6ac8f12b398f687e56927d80af1990504:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-url
 * [new ref]         38b9eea6ac8f12b398f687e56927d80af1990504 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 38b9eea Update to version 2.5.4; Fixes RHBZ#2323618