Support variables in rules: exists

What does this MR do and why?

Support variable expansion in rules: exists. This change is under the feature flag ci_variable_expansion_in_rules_exists.

Screenshots or screen recordings

When the rules match:

variables:
  PATTERN: '*.yml'
  WRONG_PATH: 'wrong.rb'
rule_exist_job:
 script: 
    - echo $PATTERN
    - echo $WRONG_PATH
    - echo $EXIST_PATH
 rules:
    - exists:
      - $PATTERN

In the example above, we have an existing deploy.yml file, so the rule_exist_job runs:

When the rules do not match:

variables:
  PATTERN: '*.yml'
  EXIST_PATH: 'upload.yml'
  WRONG_PATH: 'wrong.rb'
rule_exist_job:
 script: 
    - echo $PATTERN
    - echo $WRONG_PATH
    - echo $EXIST_PATH
 rules:
    - exists:
      - $PATTERN

There are no jobs for this pipeline:

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to: #283881 (closed)
Rollout issue: #381046 (closed)

assigned to @lauraX

added backend label

	1 Warning
⚠	60a42745: The commit subject must contain at least 3 words. For more information, take a look at our Commit message guidelines.

	2 Messages
📖	CHANGELOG missing: If you want to create a changelog entry for GitLab FOSS, add the Changelog trailer to the commit message you want to add to the changelog. If you want to create a changelog entry for GitLab EE, also add the EE: true trailer to your commit message. If this merge request doesn't need a CHANGELOG entry, feel free to ignore this message.
📖	This merge request adds or changes documentation files. A review from the Technical Writing team before you merge is recommended. Reviews can happen after you merge.

Documentation review

The following files require a review from a technical writer:

• doc/ci/variables/where_variables_can_be_used.md (Link to current live version)
• doc/ci/yaml/index.md (Link to current live version)

The review does not need to block merging this merge request. See the:

• Metadata for the *.md files that you've changed. The first few lines of each *.md file identify the stage and group most closely associated with your docs change.
• The Technical Writer assigned for that stage and group.
• Documentation workflows for information on when to assign a merge request for review.

Reviewer roulette

Changes that require review have been detected!

Please refer to the table below for assigning reviewers and maintainers suggested by Danger in the specified category:

Category	Reviewer	Maintainer
backend	Corinna Gogolok (@cwiesner) (UTC+1, same timezone as @lauraX)	Mayra Cabrera (@mayra-cabrera) (UTC-6, 7 hours behind @lauraX)

To spread load more evenly across eligible reviewers, Danger has picked a candidate for each review slot, based on their timezone. Feel free to override these selections if you think someone else would be better-suited or use the GitLab Review Workload Dashboard to find other available reviewers.

To read more on how to use the reviewer roulette, please take a look at the Engineering workflow and code review guidelines. Please consider assigning a reviewer or maintainer who is a domain expert in the area of the merge request.

Once you've decided who will review this merge request, assign them as a reviewer! Danger does not automatically notify them for you.

If needed, you can retry the 🔁 danger-review job that generated this comment.

Generated by 🚫 Danger

Proper labels assigned to this merge request. Please ignore me.

👋 @lauraX - please see the following guidance and update this merge request.

	1 Error, 1 Warning
❌	Please add typebug typefeature, or typemaintenance label to this merge request.
⚠	Please add a subtype label to this merge request.

If you have added a type label and do not feel the purpose of this merge request matches one of the subtypes labels, please resolve this discussion.

Allure report

allure-report-publisher generated test report!

e2e-review-qa: ❗ test report for cc571137

expand test summary

+-----------------------------------------------------------------------------------------+
|                                     suites summary                                      |
+------------------------------------+--------+--------+---------+-------+-------+--------+
|                                    | passed | failed | skipped | flaky | total | result |
+------------------------------------+--------+--------+---------+-------+-------+--------+
| Verify                             | 43     | 0      | 8       | 9     | 51    | ❗     |
| Create                             | 28     | 0      | 1       | 0     | 29    | ✅     |
| Manage                             | 43     | 0      | 3       | 7     | 46    | ❗     |
| Plan                               | 49     | 0      | 1       | 0     | 50    | ✅     |
| Feature flag handler sanity checks | 9      | 0      | 0       | 0     | 9     | ✅     |
| Govern                             | 10     | 0      | 5       | 0     | 15    | ✅     |
| Version sanity check               | 0      | 0      | 1       | 0     | 1     | ➖     |
| Configure                          | 0      | 0      | 1       | 0     | 1     | ➖     |
| Package                            | 0      | 0      | 1       | 0     | 1     | ➖     |
+------------------------------------+--------+--------+---------+-------+-------+--------+
| Total                              | 182    | 0      | 21      | 16    | 203   | ❗     |
+------------------------------------+--------+--------+---------+-------+-------+--------+

e2e-package-and-test: ❌ test report for cc571137

expand test summary

+---------------------------------------------------------------------------+
|                              suites summary                               |
+----------------------+--------+--------+---------+-------+-------+--------+
|                      | passed | failed | skipped | flaky | total | result |
+----------------------+--------+--------+---------+-------+-------+--------+
| Verify               | 86     | 0      | 16      | 0     | 102   | ✅     |
| Manage               | 135    | 1      | 26      | 2     | 162   | ❌     |
| Create               | 318    | 0      | 10      | 2     | 328   | ❗     |
| Package              | 0      | 0      | 6       | 0     | 6     | ➖     |
| Plan                 | 120    | 0      | 0       | 0     | 120   | ✅     |
| Fulfillment          | 4      | 0      | 30      | 0     | 34    | ✅     |
| Govern               | 82     | 0      | 0       | 2     | 82    | ❗     |
| Analytics            | 4      | 0      | 0       | 0     | 4     | ✅     |
| Configure            | 0      | 0      | 6       | 0     | 6     | ➖     |
| Release              | 10     | 0      | 0       | 0     | 10    | ✅     |
| Secure               | 14     | 0      | 2       | 2     | 16    | ❗     |
| ModelOps             | 0      | 0      | 2       | 0     | 2     | ➖     |
| Version sanity check | 0      | 0      | 2       | 0     | 2     | ➖     |
+----------------------+--------+--------+---------+-------+-------+--------+
| Total                | 773    | 1      | 100     | 8     | 874   | ❌     |
+----------------------+--------+--------+---------+-------+-------+--------+

Setting label grouppipeline authoring based on @lauraX's group.

added grouppipeline authoring label

Setting label(s) devopsverify sectionops based on grouppipeline authoring.

added devopsverify sectionops labels

added 1082 commits

• 234f1cfa...cd10caae - 1081 commits from branch master
• 1fb63829 - Support variables in rules: exists

Compare with previous version

Hi @furkanayhan! Do you think this needs a FF? I know that Marius had the rules: changes MR under a FF, but it was also the variable expansion one, so I'm not sure 🤔

marked this merge request as ready

requested review from @avielle and @marcel.amirault

added 563 commits

• 1fb63829...304c0ba5 - 560 commits from branch master
• 29a29fdc - Support variables in rules: exists
• 2e6dbf71 - Adds ci_variable_rules_exist feature flag
• 80256555 - Adds docs for rules:exists variable expansion

Compare with previous version

@avielle - could you please do the first review of this MR? I did some refactoring in order to enable the new functionality and sort of kept the refactoring for the feature flag usage. Let me know what you think.

Hi @marcel.amirault - could you please do a docs review for variable expansion in rules: exists? Thank you!

added documentation feature flag labels