Make it two plans

/plans/modified to run only in CI (where trigger=commit is set),
running just the modified tests

/plans/all if one desires to run all tests

plans.fmf

@@ -5,8 +5,21 @@ execute:
   how: tmt
 
 /modified:
+  summary: Plan executing just modified tests (only in CI)
+  enabled: false
+  adjust:
+  - when: trigger == commit
+    enabled: true
   discover:
     how: fmf
     modified-only: true
     modified-ref: reference/main
     modified-url: https://src.fedoraproject.org/tests/ruby
+    
+/all:
+  summary: For ad-hoc, local execution of these tests (disabled in CI)
+  adjust:
+  - when: trigger == commit
+    enabled: false
+  discover:
+    how: fmf