The best way to notify RB from gitlab would be a webook from gitlab to RB. I wrote a tiny wsgi application that get's "pipeline event" [1] for the project/group that calls rbt. A better approach would be to include the ability to RB itself without that wrapper script.

#!/usr/bin/python

import json
import logging
import uwsgi
import subprocess

log = logging.getLogger("gitlab")

logging.basicConfig(
    format="%(asctime)s %(levelname)s: %(message)s", level="INFO"
)


def health():
    return None


def get_state(state):
    if state == "pending":
        return ("build queued...", "pending")

    if state == "passed":
        return ("build succeeded.", "done-success")

    if state == "running":
        return ("build started...", "pending")

    if state == "canceling":
        return ("canceling build...", "pending")

    if state == "canceled":
        return ("build canceled", "error")

    return ("build failed", "error")


def process_rbtools(v, c, token):
    url = c.get("url")
    url_text = "See pipeline"

    description, state = get_state(c.get("detailed_status"))
    cmd = [
        "rbt",
        "status-update",
        "set",
        "--url",
        url,
        "--url-text",
        url_text,
        "-r",
        v.get("REVIEWBOARD_REVIEW_ID"),
        "-s",
        v.get("REVIEWBOARD_STATUS_UPDATE_ID"),
        "--server",
        v.get("REVIEWBOARD_SERVER"),
        "--api-token",
        token,
        "--state",
        state,
        "--description",
        description,
        "--disable-cookie-storage",
        "--disable-cache-storage",
    ]

    log.info(cmd)
    subprocess.check_call(cmd)
    return uwsgi.SPOOL_OK


def process_pipeline(c, token):
    if c is not None:
        v = c.get("variables")
        if v is not None:
            v = {item["key"]: item["value"] for item in v}
            if "REVIEWBOARD_SERVER" in v:
                return process_rbtools(v, c, token)
    return uwsgi.SPOOL_OK


def process_data(data):
    try:
        c = json.loads(data.get("body"))
    except (TypeError, ValueError) as e:
        log.info("Broken json: {0}".format(e))
        return uwsgi.SPOOL_OK

    # log.debug(json.dumps(c, indent=4, sort_keys=True))

    if c.get("object_kind") == "pipeline" and "object_attributes" in c:
        return process_pipeline(c.get("object_attributes"), data.get(b"token"))

    return uwsgi.SPOOL_OK


def process_spooler(data):
    try:
        return process_data(data)
    except BaseException:
        log.exception("Cannot process data")

    return uwsgi.SPOOL_RETRY


def application(environ, start_response):
    result = []
    headers = [("Content-Type", "text/plain")]

    request_body = []
    try:
        request_body_size = environ.get("CONTENT_LENGTH", 0)
        if request_body_size:
            request_body = environ["wsgi.input"].read(int(request_body_size))
    except ValueError as e:
        log.warn("Cannot read body: {0}".format(e))
        headers.append(("Content-Length", str(len(result))))
        start_response("400 Bad Request", headers)
        return result

    status = "200 OK"
    if len(request_body) > 0 and "HTTP_X_GITLAB_TOKEN" in environ:
        uwsgi.spool(
            {
                b"body": request_body,
                b"token": environ["HTTP_X_GITLAB_TOKEN"].encode("utf-8"),
            }
        )
    else:
        healthResult = health()
        if healthResult is None:
            status = "204 No Content"
        else:
            status = "503 Service Unavailable"
            result = [healthResult.encode("utf-8")]

    headers.append(("Content-Length", str(len(result))))
    start_response(status, headers)
    return result


uwsgi.spooler = process_spooler




[1] https://docs.gitlab.com/user/project/integrations/webhook_events/#pipeline-events

Also it would be a good idea to provide a gitlab component for patching like this.
templates/ref.yml
spec:
---

.reviewboard:
    reviewboard_before_script:
       - |
             if [ "$REVIEWBOARD_SERVER" != "" ]; then
                apk add rbtools git
                rbt patch --server ${REVIEWBOARD_SERVER} --diff-revision ${REVIEWBOARD_DIFF_REVISION} ${REVIEWBOARD_REVIEW_ID}
             fi




templates/global_before_script.yml
spec:
---

include:
  - component: https://github.com/reviewboard/rbintegrations/ref@main

before_script:
    - !reference [.reviewboard, reviewboard_before_script]



customer .gitlab-ci.yml
include:
  - component: https://github.com/reviewboard/rbintegrations/ref@main

first-job:
  script:
    - echo Hello