Run integration pipeline for target branch only

When we're integrating a single branch into a single manifest branch,
there is no need to run the intgeration pipeline for all configured
integrations, but only for those that match the target branch of the
current merge request.

manifest-integration-pipelines.yml.jinja2

@@ -35,10 +35,13 @@ generate:
     # to explicitly pass any of them as command line arguments.
 {% for integration in INTEGRATION.split('\n') %}
 {% set SOURCE_BRANCH, TARGET_PROJECT, TARGET_BRANCH = integration.split(':') %}
+{% if SOURCE_BRANCH == CI_MERGE_REQUEST_TARGET_BRANCH_NAME ||
+      SOURCE_BRANCH == CI_COMMIT_REF_NAME %}
     - TARGET_PROJECT={{ TARGET_PROJECT }}
         .gitlab-ci/scripts/generate_job_from_template.py
         --template=.gitlab-ci/manifest-integration-jobs.yml.jinja2
         > manifest-integration-jobs-{{ loop.index }}.yml
+{% endif %}
 {% endfor %}
   artifacts:
     expire_in: 4 weeks
@@ -50,6 +53,8 @@ generate:
 # --------------------------------------------------------------------------------------
 {% for integration in INTEGRATION.split('\n') %}
 {% set SOURCE_BRANCH, TARGET_PROJECT, TARGET_BRANCH = integration.split(':') %}
+{% if SOURCE_BRANCH == CI_MERGE_REQUEST_TARGET_BRANCH_NAME ||
+      SOURCE_BRANCH == CI_COMMIT_REF_NAME %}
 
 {{ TARGET_PROJECT }}:{{ TARGET_BRANCH }}:
   stage: infrastructure
@@ -72,4 +77,5 @@ generate:
       job: generate
     strategy: depend
 
+{% endif %}
 {% endfor %}