$ git clone -n https://src.fedoraproject.org/rpms/perl-Alien-Libxml2.git /var/lib/mock/f40-build-732643-104925/root/chroot_tmpdir/scmroot/perl-Alien-Libxml2
Cloning into '/var/lib/mock/f40-build-732643-104925/root/chroot_tmpdir/scmroot/perl-Alien-Libxml2'...
$ git fetch origin 40aaed2c3e7c479e607a9f080a42936d6449f490:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Alien-Libxml2
 * [new ref]         40aaed2c3e7c479e607a9f080a42936d6449f490 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 40aaed2 Rebuild against libxml2-2.11.5 (rhbz#2232594)