Don't launch a job if the only changes are on a folder - gitlab

Question

I want to disable some jobs if the only changes that happen in last git commit are in a docs folder. The idea is to be able to push new documentation on master (in a docs folder) without launching jobs responsible for pushing to production.
What I tried:
prod:
script:
- whatever
rules:
- changes:
- docs/*
when: never
It does not work because I want to be able to launch this job if there are changes in docs AND other files.
I also tried with a regular expression (probably wrong) but it does not seem to be taken in charge by gitlab. Something like that:
prod:
script:
- whatever
rules:
- changes:
- (docs/*)!*
when: never
I also tried a suboptimal solution, with a CI variable $CI_COMMIT_MESSAGE:
prod:
script:
- whatever
rules:
- if: $CI_COMMIT_MESSAGE == "doconly"
when: never
and it does not work, except if the variable is set manually. Or this:
prod:
script:
- whatever
except:
variables:
- if: $CI_COMMIT_MESSAGE == "doconly"
I also tried with a bash script that would set up a variable but variables can't be passed between jobs.
Here the bash script:
LAST_COMMIT=$(git log --pretty=format:'%H' -n 1)
FILES=$(git diff-tree --no-commit-id --name-only -r ${LAST_COMMIT})
doconly=true
while read -r line && $doconly; do
if [[ ! "$line" =~ docs/* ]] ; then
doconly=false
exit 1
fi
done <<< "$FILES"
exit 0