Git Cheat Sheets

Included in development Git

2020-05-01 687 words 4 minutes

Contents

GitLab

Gitlab CI-CD

Reference

Pay attention that the correct file for gitlab ci-cd pipeline .gitlab-ci.yml ends with .yml, not .yaml.

Choose which executor for gitlab runner

Increase concurrent jobs

Jobs are executed by Runners. Multiple jobs in the same stage are executed in parallel, if there are enough concurrent runners.

The limit of concurrent jobs are tunable in config.toml.

Job image vs docker executor

In the definition of jobs, the image keyword is the name of the Docker image the Docker executor will run to perform the CI tasks.

Check if other executors like ssh can consume the image keyword

Services in jobs

The services keyword defines just another Docker image that is run during your job and is linked to the Docker image that the image keyword defines. This allows you to access the service image during build time. This feature is designed to provide network accessible services. A database is the simplest example of such a service. Do not use services as tools for the jobs.

Semantic versioning

Semantic release allows automatic versioning and package publishing. How does it work?

Follow Angular commit message convention during development phase
Host code in a git repository
Create a working CI pipeline, i.e. add a working .gitlab-ci.yml file to project
Install git 2.7.1 minimum, node.js 10.18 minimum and semantic-release in CI environment. These tools can be installed in a job of Jenkins runner, or be ready with a Jenkins runner based of node.js image
Configure CI service to expose the access token in the environment variable and run semantic-release during the versioning job
Add configuration file
- include branches
- include plugins (depending on CI environment)
Trigger the CI pipeline

Debugging in gitlab runners

Run gitlab-runner in debug mode:
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gitlab-runner --debug run
Use Interactive Web Terminals
- Support for Docker executor is underway
Gitlab has numerous built-in environment variables for the pipeline runtime. Take advantage of them.

Troubleshooting

Nested reference of variables is not working in gitlab-ci.yml.

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$ cat .gitlab-ci.yml

variables:
  PROJECT_NAME: $CI_PROJECT_NAME # default CI variable of gitlab

job-sample:
  stage: stage-sample
  image: docker
  variables:
    BUILD_PROJECT_NAME: $PROJECT_NAME # Don't. $CI_PROJECT_NAME will not be evaluated here
  services:
    - docker:dind
  script:
    - echo $BUILD_PROJECT_NAME # Don't. Output result: $PROJECT_NAME
    - echo $PROJECT_NAME # Do. Output result: git-cheat-sheet-and-tricks

Mirroring using deploy keys

Git service providers have a mirroring functionality, allowing a repository either to push to or pull from a mirror.

However, in case mirroring is impossible due to software version or a network policy, a cron job or a CI pipeline with runners like Jenkins can be useful.

In order to register deploy keys in the target mirror, several steps are to follow:

Firstly generate your SSH keys locally:

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ssh-keygen -t rsa -C "your.email@address.com" -b 4096

Assign public key id_rsa.pub (from ssh-rsa to end of your email) to the target git project, option Create a new deploy key in Project Settings. Ensure write permission is selected.

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# Downloads and installs xclip. If you don't have `apt-get`, you might need to use another installer (like `yum`)
sudo apt-get install clip
# Copies the contents of the id_rsa.pub file to your clipboard
xclip -sel clip < ~/.ssh/id_rsa.pub

Add the private SSH_KEY to the environment variable of your repository setting and let the CI/CD pipeline or your cron job does its work :).

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apt update && apt-get install -y openssh
mkdir ~/.ssh
eval `ssh-agent -s` # start ssh-agent before adding key
cat $SSH_KEY | ssh-add - # adding ssh key without using sensitive round brackets
echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config # no strict key checking
git config --global user.name "Your Name"
git config --global user.email "your.email@address.com"
git checkout master
git pull --unshallow origin master # pull old tree deeply to ensure we have all new changes
git remote add remote git@github.com:new/repo.git || true
git push -u remote master

Registration/unregistration of GitLab runners

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gitlab-runner list
gitlab-runner unregister --url http://gitlab.example.com/ --token t0k3n
gitlab-runner unregister --name test-runner
gitlab-runner unregister --all-runners