## Summary `rules: changes` is triggering in merge request pipelines when a matching file is changed but then changed back. ## Problem - I make a branch and MR, with a job containing `rules: changes: ["my_file.txt"]` - I make commits that do not change `my_file.txt`.  The job **does not** run (as expected). - I make a commit changing `my_file.txt`. The job **does** run (as expected). - I make another commit _undoing_ the change to `my_file.txt`.  The job **does** run still (_unexpected!_) This behavior is unexpected because [the documentation](https://docs.gitlab.com/ci/yaml/#rules) clearly states: > Merge request pipelines, rules:changes compares the changes with the target MR branch. ### Current workarounds and why they fall short A solution I've found for this problem is to simply use `compare_to: $CI_MERGE_REQUEST_TARGET_BRANCH`. However, this fall short because it shouldn't be necessary. [The documentation](https://docs.gitlab.com/ci/yaml/#rules) clearly states: > Merge request pipelines, rules:changes compares the changes with the target MR branch. ### Example jobs Here is an example job definition in `.gitlab-ci.yml` that reproduces the issue: ```yaml rules-changes-test: script: - echo "foo bar" rules: - if: '$CI_PIPELINE_SOURCE == "merge_request_event"' changes: - my_file.txt ``` And here's how the issue can be "fixed": ```yaml rules-changes-test: script: - echo "foo bar" rules: - if: '$CI_PIPELINE_SOURCE == "merge_request_event"' changes: paths: - my_file.txt compare_to: $CI_MERGE_REQUEST_TARGET_BRANCH_NAME ``` ## Expected Behavior I expect that using `compare_to: $CI_MERGE_REQUEST_TARGET_BRANCH` and not using `compare_to` at all should be equivalent. ## Proposed Solutions - Fix `rules: changes` when not using `compare_to` so that it behaves as expected - Fix the documentation to state clearly and accurately how the `diff` used by `rules: changes` is computed - Provide a `$CI_` environment variable that lists the files in the diff (currently a full diff is available through the API, however this is more than desired and inconvenient to get). ## Environment - GitLab.com (SaaS) - Affects any project using `rules: changes` without `compare_to` in ## Links - https://docs.gitlab.com/ci/yaml/#rules