$ git clone -n https://src.fedoraproject.org/rpms/jakarta-activation.git /var/lib/mock/f42-build-3356269-45027/root/chroot_tmpdir/scmroot/jakarta-activation
Cloning into '/var/lib/mock/f42-build-3356269-45027/root/chroot_tmpdir/scmroot/jakarta-activation'...
$ git fetch origin 39bbc87dca84ef2e7d9b658a8fbe064be3add56f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/jakarta-activation
 * [new ref]         39bbc87dca84ef2e7d9b658a8fbe064be3add56f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 39bbc87 Remove javadoc subpackage