Bug with quotes in quotes and scripts

Hi,

I have the following in my gitlab-ci.yml (I removed what I think are unimportant lines):

variables:
  MVN: "mvn --errors -B -U -Dmaven.repo.local=m2cache"
  MVN_BUILD: "$MVN -Pjacoco -DaltDeploymentRepository='staging::default::file:staging'"

...

build-test-backend:
  <<: *mvn-java-8
  stage: build
  script:
    - "apk update && apk add git"
    - "git clone --depth 1 https://github.com/victornoel/jersey-pac4j"
    - "echo MVN_BUILD=$MVN_BUILD"
    - "$MVN_BUILD clean deploy"
    - "$MVN_BUILD -f jersey-pac4j clean deploy"
    - "$MVN_BUILD -f backend clean deploy"
    - "ls"
  artifacts:
    paths:
      - staging

And when I look at the logs, I see the following:

$ echo MVN_BUILD=$MVN_BUILD
MVN_BUILD=mvn --errors -B -U -Dmaven.repo.local=m2cache -Pjacoco -DaltDeploymentRepository='staging::default::file:staging'
...
[INFO] Using alternate deployment repository 'staging::default::file:staging'

And the thing is that there should be written: Using alternate deployment repository staging::default::file:staging without the quotes (that's what actually happens locally on my machine if I execute the same command. In this particular case, it is unfortunate because it creates a directory named staging' instead of staging (that's how I realised there was something fishy :).

I guess I can mitigate this problem by not using quotes (I don't really need to in this specific case), but I guess there is other cases where it could be problematic.