Git Hub/Lab Syncing Ideas

git{hub,lab}-sync.md

General Setup

• Get GitLab admin user details
• Get GitLab sync user details
• Get GitHub admin user details

GitHub -> GitLab Sync Setup

1. Select source GitHub repo
2. Either: Select/create destination GitLab repo
3. Clone 1. add remote 2.
4. Check branches on 1,2 are consistent/fast-forwardable (or 2 is empty)
5. Enable builds on 2. select a builder.
6. Generate a ssh keypair.
7. Install private key to secret build variable on 2.
8. Install public key to GitLab sync user.
9. Grant GitLab sync user Developer permissions to 2.
10. Create a trigger on 2.
11. Update .gitlab-ci.yml with git sync CI task
12. Commit and push repo to both.
13. Install webhook for trigger on 1. (with GitHub trigger source variable)

GitLab -> GitHub Sync Setup

In the above procedure, insert: After step 8:

• Install public key to GitHub repo as Deployment Key with write permissions.

Intended Flows

GitHub -> GitLab

1. Push to GitHub
2. GitHub webhook calls out to GitLab build trigger
3. GitLab spawns build tasks including/not-excluding the "triggers" pattern.
4. Git sync task executes (in GitHub mode).
5. GitLab version of repository at some unspecified revision/branch is checked out automatically.
6. Spawn ssh-agent with the stored private key.
7. Add GitHub remote and fetch.
8. Fast-forward each GitHub branch into the corresponding GitLab branch, creating if required.
9. If any changes made, push to GitLab. (This build task ends).
10. GitLab receives push and starts standard build process.
11. GitLab executes GitLab->GitHub sync task as part of the standard build, it should be idempotent.

GitLab -> GitHub

1. Push to GitLab
2. GitLab spawns build tasks.
3. Git sync task executes (in GitLab mode).
4. GitLab version of repository at some current revision/branch is checked out automatically.
5. Spawn ssh-agent with the stored private key.
6. Add GitHub remote and fetch.
7. Fast-forward each GitLab branch into the corresponding GitHub branch, creating if required.
8. If any changes made, push to GitHub. (This build task ends).
9. GitHub receives push, triggers GitLab webhook, the resulting push should be idempotent.

Limitations

• Force pushes on any repo will break the sync, good motivation to forbid them.
• All normal build tasks will need to be marked as excluding triggers, ones that need to be triggered need special handling, with build variables to select correct mode.