Disable expansion of file type variables when referenced in child pipelines

Summary

Since 15.7, file type variables should expand to the filename instead of the file content. However, in child pipelines, the file content is still expanded

Steps to reproduce

Triggering project

Setup

• Configure a file type variable $MAVEN_SETTINGS with random string content (here <settings>test</settings>)

.gitlab-ci.yml

variables:
  MAVEN_CLI_OPTS: >-
   -s $MAVEN_SETTINGS
   --batch-mode
   -Pgitlab-cicd

build-job:
  stage: build
  script:
    - echo "$MAVEN_SETTINGS"
    - cat "$MAVEN_SETTINGS"

release:
  stage: deploy
  trigger:
    project: triggered-project

The build job produces the expected output, expanding the file name

Triggered project

.gitlab-ci.yml

build-job:
  stage: build
  script:
    - echo "$MAVEN_CLI_OPTS"
    - cat "$MAVEN_CLI_OPTS"

Job log

$ echo "$MAVEN_CLI_OPTS"
-s <settings>test</settings> --batch-mode -Pgitlab-cicd
$ cat "$MAVEN_CLI_OPTS"
cat: invalid option -- ' '

What is the current bug behavior?

file type variable expands file content in child pipeline

What is the expected correct behavior?

file type variable expands file path in child pipeline

Output of checks

This bug happens on GitLab.com

Proposal

Look into Ci::Bridge#calculate_downstream_variables and you may see that we call ExpandVariables.expand in the sub-methods.

Here is the original MR that introduced this feature.