$ git clone -n https://src.fedoraproject.org/rpms/rubygem-gobject-introspection.git /var/lib/mock/f40-build-2639136-66340/root/chroot_tmpdir/scmroot/rubygem-gobject-introspection
Cloning into '/var/lib/mock/f40-build-2639136-66340/root/chroot_tmpdir/scmroot/rubygem-gobject-introspection'...
$ git fetch origin d2fe164fbebe5c658679c449aa3abdba367535ae:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-gobject-introspection
 * [new ref]         d2fe164fbebe5c658679c449aa3abdba367535ae -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d2fe164 remove patch