.tekton: disable build on merged commit

We let Jenkins triggers the build manually instead of building asking
Pipeline-as-Code to do it on file changes. See [1] for more details.

[1] https://github.com/coreos/fedora-coreos-tracker/issues/2241

.tekton/templates/streams.yaml

@@ -33,8 +33,6 @@ streams:
 
   - name: rawhide
     has_overrides: true
-    # rawhide on-push only triggers when .tekton/trigger file changes
-    on_push_cel_expression: 'event == "push" && target_branch == "rawhide" && ".tekton/trigger".pathChanged()'
 
   - name: branched
     has_overrides: true

ci/generate-tekton-pipelinerun.py

@@ -25,7 +25,6 @@ except ImportError as e:
 EVENT_CONFIGS = {
     "on-push": {
         "cancel_in_progress": False,
-        "cel_expression_base": 'event == "push" && !(files.all.all(f, f.matches("ci/buildroot/") || f.matches(".tekton/fcos-buildroot/")))',
         "output_image_suffix": ":{{revision}}",
         "image_expires_after": None,
     },
@@ -73,6 +72,8 @@ def generate_pipelinerun(
     # Check for custom CEL expression for on-push event
     if event_type == "on-push" and "on_push_cel_expression" in stream_config:
         cel_expression = stream_config["on_push_cel_expression"]
+    elif "cel_expression_base" not in event_config:
+        cel_expression = f'"false"'
     else:
         # Build the CEL expression with stream-specific branch filter
         cel_expression = f'{event_config["cel_expression_base"]} && target_branch == "{stream_name}"'