$ git clone -n https://src.fedoraproject.org/rpms/rust-serde_derive.git /var/lib/mock/f39-build-1494673-34542/root/chroot_tmpdir/scmroot/rust-serde_derive
Cloning into '/var/lib/mock/f39-build-1494673-34542/root/chroot_tmpdir/scmroot/rust-serde_derive'...
$ git fetch origin 793f0fd8e45cff109818275b63d9e380c101c390:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-serde_derive
 * [new ref]         793f0fd8e45cff109818275b63d9e380c101c390 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 793f0fd Update to version 1.0.189; Fixes RHBZ#2243780