serdroid

- 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:xxxxxxxxxxxxxxxxxxxx@example.com/gitlab-examples/ci-debug-trace.git
# should be git@example.com:/gitlab-examples/ci-debug-trace.git
    - export PUSH_REPO=$(echo "$CI_REPOSITORY_URL" | sed -e "s|.*@\(.*\)|git@\1|" -e "s|/|:/|" )