During the initial puppetsync of SIMP-8139, the projects' Gitlab CI pipelines included the spec and acceptance test matrix, despite the the .gitlab-ci.yml not listing any of the changes files in the relevant changes: rule.
Interesting clues in https://gitlab.com/simp/pupmod-simp-sudo/-/pipelines. It appears that the rules: changes: may be calculated against files changed in parent commits―not just the present commit:
Following the SIMP-8139 branch, (where commits never updated any of the files tracked by rules: changes:):
The pipeline matrix triggered on the first commit (prompting this issue)
Subsequent force-pushes (correctly) did not trigger the matrix
80891d57: Another PR was merged into the master branch that did update files that should trigger rules: changes
Note: In the pipeline diagram above, the master update looks more recent than all the other commits because due the delay
327ff5d8: The pipeline matrix triggered in the next force push (made on top of the latest master, so the parent commit became 80891d57)
Note that none the files in commit 327ff5d8 changed any files that should trigger the rules: changes:―but the rule triggered anyway once 80891d57 merged into the master branch and became its parent commit.