systemd instantiated services are not started when enabled via ignition

[redbaron]

Bug

Instantiated services can be enabled and return no error, but when machine boots, service is not enabled:

systemd:
  units:
    - name: echo@.service
      contents: |
        [Unit]
        Description=f
        [Service]
        Type=oneshot
        ExecStart=/bin/echo %i
        [Install]
        WantedBy=multi-user.target
    - name: echo@foo.service
      enable: true

then boot, see systemctl status echo@foo.service and it shows that it didn't start.

Container Linux Version

NAME="Container Linux by CoreOS"
ID=coreos
VERSION=1520.8.0
VERSION_ID=1520.8.0
BUILD_ID=2017-10-26-0342
PRETTY_NAME="Container Linux by CoreOS 1520.8.0 (Ladybug)"
ANSI_COLOR="38;5;75"
HOME_URL="https://coreos.com/"
BUG_REPORT_URL="https://issues.coreos.com"
COREOS_BOARD="amd64-usr"

Expected Behavior

Enabled service starts

Actual Behavior

Ingition uses systemd presets, which apparently does not support enabling instantiated services.
There is this discussion https://lists.freedesktop.org/archives/systemd-devel/2015-August/033834.html where hack with explicit symlinks installed via Alias= are used. Would be nice if Ignition took care of it

[coreosbot]

Moved to coreos/ignition#586.