create commit and push to repo during CI build in gitlab

gistfile1.txt

- generate ssh key for gitlab-runner user
- add ssh key to project's deploy keys (project/setting/repository)

add below commands into script section of .gitlab-ci.yml file.
# CI_REPOSITORY_URL contains gitlab-ci-token. replace start of the string up to '@'  with git@' and append a ':' before first '/'
# example 
# CI_REPOSITORY_URL=https://gitlab-ci-token:[email protected]/gitlab-examples/ci-debug-trace.git
# should be [email protected]:/gitlab-examples/ci-debug-trace.git
    - export PUSH_REPO=$(echo "$CI_REPOSITORY_URL" | sed -e "s|.*@\(.*\)|git@\1|" -e "s|/|:/|" )
# gitlab-runner runs on a detached HEAD, checkout a new branch
    - git checkout -b lock
#generate & save dependencies.lock file
    - gradle generateLock saveLock
# commit dependencies.lock file. add '[skip ci]' into commit message to prevent CI infinite loop
    - git commit -m '[skip ci] add auto generated dependencies.lock' dependencies.lock
# set remote push URL
    - git remote set-url --push origin "${PUSH_REPO}"
# push changes to originating branch
    - git push origin lock:${CI_COMMIT_REF_NAME}