Why jobs running with set "only" keyword? - gitlab-ci

Question

I tried to spice my gitlab gitflow with gitlab-cicd. My goal is to create a job which is running while a merge request and check if the source branch for this merge request is either a hotfix/* or release/* branch. A simple bash script is in charge for this:
#!/bin/bash
if [[ "$1" =~ ^hotfix/* ]]; then
echo "Begin Hotfix Merge"
exit 0
else
echo "ERROR: Directory does not exist."
exit 1
fi
where $1 is the predefined variable CI_MERGE_REQUEST_SOURCE_BRANCH_NAME as argument of the script.
My .gitlab-ci.yaml looks the following:
image: ubuntu:latest
stages:
- test
workflow:
rules:
- if: $CI_PIPELINE_SOURCE == "merge_request_event"
- if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
test1:
tags:
- docker
- linux
stage: test
script:
- echo "Do a test here"
- echo "For example run a test suite"
- echo $PWD
- ls -la .gitlab/
job1:
tags:
- docker
- linux
script:
- echo "This job runs in merge request pipelines"
- echo $PWD
- ls -la .gitlab/workflow-scripts/
- echo "$CI_MERGE_REQUEST_SOURCE_BRANCH_NAME"
- bash ./.gitlab/workflow-scripts/check_sourcebranch.sh "$CI_MERGE_REQUEST_SOURCE_BRANCH_NAME"
only:
- merge_requests
- master
I am not shure if the workflow:rules distrubs anything. If I now start a merge request the pipeline runs without any issues inside the merge request, but if I aprove the request and the pipeline gets triggered again, both jobs are running.
Any Idea, why job1 is triggered, even with the only rule?
EDIT: I removed the part with the unexpected error. This Error was a residual of a classic copy&pasta and was actually expected in this scenario.

Answer 1

Fixed job for testing branch name on MR:
stages:
- tests
image: ubuntu:latest
test-mr-branch-name:
stage: tests
only:
- merge_requests
tags:
- docker
- linux
script:
- |
if [[ ! "${CI_MERGE_REQUEST_SOURCE_BRANCH_NAME}" =~ ^(hotfix|release)\/.+$ ]]; then
echo "ERROR: Wrong Merge!"
exit 1
fi
p.s. Operator between values of only tag is or. Read me.
p.s. You may set multiline bash script in Gitlab CI.