$ git clone -n https://src.fedoraproject.org/rpms/rubygem-gtksourceview3.git /var/lib/mock/f39-build-1502636-34934/root/chroot_tmpdir/scmroot/rubygem-gtksourceview3
Cloning into '/var/lib/mock/f39-build-1502636-34934/root/chroot_tmpdir/scmroot/rubygem-gtksourceview3'...
$ git fetch origin cf4725e9233517ff192158a52bebeea53f69ae9c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-gtksourceview3
 * [new ref]         cf4725e9233517ff192158a52bebeea53f69ae9c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cf4725e 4.2.0 entry