fix: triggering gitlab pipeline on tags (#717)

I noticed that if we trigger Gitlab pipeline from a tag, the action
fails. And if we trigger it from a branch, the Docker image tags are
weird. So we should trigger it from a tag from the release branch and
from branch (push) from develop and master.

.github/workflows/trigger-gitlab-pipeline.yml

@@ -23,11 +23,15 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Sync HEAD with GitLab
-        uses: saderi/push-to-gitlab@v1
-        with:
-          gitlab_repository: 'gitlab.com/kiltprotocol/kilt-node'
-          gitlab_token: ${{ secrets.KILTBOT_PUSH_ACCESS_TOKEN  }}
+      - name: Config Gitlab env
+        run: |
+          git config --global user.name "github-actions[bot]"
+          git remote add gitlab https://oauth2:${{ secrets.KILTBOT_PUSH_ACCESS_TOKEN }}@gitlab.com/kiltprotocol/kilt-node
+
+      - name: Push latest ref (branch or tag)
+        run: git push gitlab ${{ github.ref_name }}
+        # It can happen that the Gitlab mirror is updated in the meanwhile, and the ref already exists there, so we ignore the error.
+        continue-on-error: true
 
       - name: Trigger GitLab CI
         run: |