## Development process

| If you want to contribute to the Eclipse ESCET project, please refer to the specific contributing information. Most of the information on this page will however also be applicable to and relevant for contributors, but not all of it.

The Eclipse ESCET project primarily uses GitLab for its development:

- Eclipse ESCET GitLab

### Issue tracking

It is often a good idea to first discuss new ideas and features with the rest of the project developers, i.e., the project committers and the project community. Discussions can take place via GitLab issues. This is especially important for radical new ideas and new features that have not been discussed before. But even if extensive discussion is not expected, as well as for obvious bugs, it is recommended to always create the issue before starting to implement a solution. This way, the community knows you are working on the issue.

When creating an issue, take the following into account:

- Since the website repository does not have its own issue tracker, issues for the website should be made on the main repository.

- An issue must be created in the issue tracker for all development, however small. This ensures we can link issues can commits to keep track of everything.

- Issues are ideally kept relatively small in scope. Bigger tasks can be split up into multiple issues, and follow-up issues can be created as needed. This allows to separate concerns, and also to work in a more agile way, e.g.:

  - Issues can be addressed more quickly.

  - Merge requests can be reviewed more easily as they are not as big.

  - Merge conflicts are less likely to occur, as branches are smaller and have a shorter lifespan.

- If a new feature is split up into multiple issues, the issues can be linked to each other. Issues can also be linked together for other reasons, e.g. if an issue requires that another issue is addressed first. See the Linked issues section of the issue.

- Attach the appropriate predefined labels to the issue:

  - Each issue should have a 'Type' label. Most issues either aim to address something that is broken ('Bug' label) or aim to add something, improve it, etc ('Enhancement' label). Removal of deprecated and obsolete functionality, code, documentation, etc is also considered an enhancement. Besides that, there are also two other 'Type' labels: 'Overview' for overview issues that keep track of progress and status of larger topics, and 'Question' for questions from users.

  - Add all relevant component labels (e.g. 'Chi' and 'CIF' labels). Typically at least one such label should be present, but it is also possible to add multiple labels if the issue involves multiple components. The components correspond to the directories in the root of our main Git repository.

  - The Eclipse ESCET project committers can add the 'Help Wanted' label to an issue to indicate that they don’t have the time to work on the issue, and that help from the community is wanted.

  - If you don’t have permissions to add the labels, the project committers will add them. If they forget, you can remind them via a comment.

### Releases and milestones

For every software version a GitLab milestone is created, to track its scope and progress. An issue is assigned to a GitLab milestone (typically the current work-in-progress one) when someone starts working on an issue, plans to do so shortly, or when someone considers the issue as something that must be addressed for that software version. Issues being worked on that can’t be resolved before the final release of that version are moved to the next version.

A single GitLab milestone is used per software version. Each software version has one or more milestone releases (`M1`, `M2`, etc), followed by one or more release candidates (`RC1`, `RC2`, etc), and is completed by a final release.

See also:

- Eclipse ESCET GitLab milestones

- Eclipse ESCET GitLab unassigned issues

### Working on issues

The process to work on issues is as follows:

- Unassigned issues can be picked up.

- Assign yourself to the issue when you are working on an issue, such that others won’t start working on it as well. You then 'own' the issue and nobody should work on the issue without discussing with you first.

  As a contributor, you can’t assign yourself to an issue. In that case, you can discuss with the project committers through issue comments, and they can assign you to the issue.

- Set the issue’s milestone to the current work-in-progress version.

- Unassign yourself if you are no longer working on an issue, don’t plan to continue, and the issue is not finished. A contributor can ask the project committers to be unassigned.

- Don’t unassign yourself after finishing the issue. It is enough to close the issue. The issue may also be closed automatically when an associated merge request is merged.

### Working with branches

The Eclipse ESCET project’s main repository roughly follows the GitFlow branching model. The `master` branch is thus for released content only, and the current development status is captured in the `develop` branch.

If possible, we approach the somewhat heavy GitFlow branching model in a practical way, reducing overhead. We may for instance skip release branches, merging `develop` to `master` directly.

When creating and working with branches, consider the following:

- Always work in a branch for the issue. Use a merge request from a feature branch to merge your changes to `develop`. Direct commits to the `develop` branch have been disabled.

- Ideally address each issue in a separate branch. This makes it easier to keep track of things. It also makes it easier for reviewers.

- Branches for work on issues (feature branches) should be relatively short lived. This makes it easier to keep the overview, allows for more agile development and faster reviews, and reduces the chance for merge conflicts.

- The GitFlow branching model allows for sub teams that share work but don’t push that to 'origin' (yet). It also allows feature branches that live only locally on a developer’s PC and not on 'origin'. To be transparent, Eclipse Foundation open source projects don’t do this. We push to our GitLab server regularly, to ensure that the community can see what the project committers are working on.

- We have no strict branch naming rules. You can let GitLab create the branch for the issue. For an issue with number #2 named 'Test', it will create a branch named `2-test`. This starts with the issue number, which makes it easy to relate a branch to an issue, without having to look inside the branch for commits (if there even are any). It also includes the issue name, which is convenient as it indicates what the branch is about, without having to look up the issue.

- There are many ways to create a branch.

  For project committers, one way to create a branch is from the GitLab issue. On the web page for a GitLab issue, there is a Create merge request button. Select the arrow to the right of it to show more options. Select Create branch. Adapt the Branch name and Source as needed. Typically the defaults suffice. Click the Create branch button to create the branch.

  For contributors, see the contributing section for the recommended approach.

- We prefer not to create a draft merge request with the creation of the branch, as then commits in the branch lead to commits on the merge requests, which lead to notification emails. Instead, work in the branch until it is ready for review, and then create a merge request for it.

- The person that is assigned to an issue 'owns' that issue, and may create branches for it. They then also 'own' those branches, and nobody should commit in those branches unless discussed with and agreed to by the branch owner.

- A branch owner may perform a rebase on a branch. However, this should be carefully considered, taking into account Git’s well-known 'Golden Rule of Rebasing'. Only perform a rebase if you understand the potential pitfalls of rewriting history. Never rebase a branch that is shared with others that have been given 'permission' to work on the branch as well. Never rebase a branch when other branches are based on it. Never rebase a branch once a merge request is created for it, e.g. to avoid confusion for reviewers, and to prevent rewriting history in case a snapshot of the merge request is submitted to the Eclipse Foundation IP team via IPLab. A safer alternative to rebasing is merging, which leads to an extra merge commit and a more complicated history. If you fully understand rebasing and employ it carefully, it can be a powerful to maintain a simpler and cleaner history. Rebasing local commits that have not yet been pushed to the remote public repository is always at your own discretion.

The website repository has only a single branch named `master`. New website versions are deployed from the build of the main repository. Changes should therefore be made to the main repository, rather than directly to the website repository.

### Commits

Consider the following regarding commits:

- Project committers working on an issue in a branch must commit regularly, to allow the other project committers and the rest of the community to see what they’re working on. This is mandatory as per the Eclipse Foundation transparency principle.

- If a branch involves significant changes, consider using multiple commits that may be easier to review. This is especially useful when renaming directories, files, methods, etc, or moving them. Typically renames and moves should be done in separate commits, without any other changes in them. The same goes for large scale code reformatting, whitespace changes, etc.

- As is standard for Git commits, the first line of the commit message must be a short summary, and must not exceed 72 characters.

  For the Eclipse ESCET project, this line must start with the issue number, to allow GitLab to link commits to issues. For instance `#NNN Commit summary.` for issue `NNN`. In case a commit relates to multiple issues, list each of them, e.g. `#1 #2 Commit summary.` for issues 1 and 2. Merge commits are exempt from this rule.

- All commits must adhere to the requirements as defined by the Eclipse Foundation. See Git Commit Records in the Eclipse Foundation Project Handbook.

If you are not an Eclipse ESCET project committer with write access to our Git repository, see the information on contributing to the Eclipse ESCET project.

To push a commit to the official Eclipse ESCET Git repo, or to your private fork in the Eclipse Foundation GitLab, you’ll be asked for your credentials. Assuming you have 2-factor authentication (2FA) enabled for your Eclipse Foundation GitLab account, use your GitLab username and a GitLab access token (not your password).

### Merge requests

Once the work on an issue is done and pushed to a branch, it must be reviewed before it is merged back. Reviews are done via merge requests. Merge requests are only accepted for the main repository, not for the website repository.

The process is as follows:

- Create a merge request for merging the branch. You can create a merge request from the Eclipse ESCET Gitlab Branches page. Select the Merge request button next to the branch to be merged.

  - Typically a branch is created from and merged back to the `develop` branch, but this can be changed if needed.

  - Start the merge request title with the related issue number(s), to allow easier tracking of merge requests back to issues.

  - If you include `Closes #NNN` in the description of the merge request, with `NNN` an issue number, that issue will automatically be closed once the merge request is merged. Use `Addresses #NNN` instead, if the merge request addresses part of the issue, but work remains, to prevent the issue from being closed. Always include either of them to ensure the merge request is properly linked to the issues it addresses. Include multiple of them if appropriate.

  - It is not mandatory to select assignees, reviewers, etc.

- The merge request is reviewed by the (other) Eclipse ESCET project committers.

- Improvements are made as necessary, reviewed again, etc, until the branch is considered to be ready to merge.

- Ensure the merge request is successfully built on Jenkins.

  - Jenkins builds merge requests separately from branches. It regularly scans the project for new merge requests and new commits to existing merge requests, but you can also force a build for the merge request. This may also be necessary if Jenkins seems stuck while Checking pipeline status.

  - Ensure the last commit to the merge request is built, to allow merging the merge request.

- Merge the branch:

  - Make sure the Delete source branch option is selected.

  - Wait for the builds on Jenkins to successfully complete and press Merge. Alternatively, press Merge when pipeline succeeds to automatically merge the merge request once the build succeeds.

- If the branch fully addressed the associated issue or issues, it/they should be closed.

If you are not an Eclipse ESCET project committer with write access to our Git repository, see the information on contributing to the Eclipse ESCET project.

### Collaborating with contributors on a merge request

During a review of a contributor’s merge request, the project committers may provide some feedback on how to improve the contribution. While contributors could address any review comments themselves, sometimes it is useful to collaborate with the project committers on a contribution.

There are two approaches to this. The first approach is simple. It has some restrictions, but suffices in most cases. The second approach is more advanced and does not suffer from those restrictions. It is however considerably more complex and cumbersome to apply and should thus only be used if necessary.

#### Simple approach

The first and simplest approach is to make sure Allow commits from members who can merge to the target branch is enabled when creating a merge request as a contributor. This way the Eclipse ESCET project committers get write access to the source branch of the merge request in the contributor’s forked repository. As the contributor and project committers then all have write access to the branch, it is easy to collaborate on the merge request.

#### Advanced approach

The simple approach is not sufficient if multiple contributors want to collaborate with the project committers on a single merge request. The contributors will each have write access to their own forked repositories, but not to the forks of the other contributors. There is no single repository where the multiple contributors and the project committers have write access.

The second approach resolves this issue, but is much more complex and cumbersome to apply. The solution is for the project committers to create a new branch in the official Git repository, based on a contributor’s branch from their forked repository. The project committers can then make changes and push them to the official Git repository. Multiple contributors can then merge those changes into their own branches in their own forked repositories. Contributors can then add their own changes again and push those to their own branches. The project committers can merge those changes into the branch on the official Git repository, make changes of their own, push those changes, etc. This can be repeated until the work is done and everything is in the branch used by the project committers. The project committers can then merge their branch into the `develop` branch of the official Git repository, via a merge request. This process works for any number of contributors. Some alignment between all parties involved is typically desired to e.g. prevent merge conflicts.

Note that you will get emails about new commits being pushed to merge requests, if you have notifications enabled for it. For branches without merge requests there is no way to get emails informing about new commits being pushed. It can thus be useful to have merge requests for all branches used by committers and contributors. Alternatively, others can be informed by posting comments on the original merge request created by the original contributor. This can prevent an overload of related merge requests and discussions being fragmented among them.

#### Fork collaboration script support

To make it easier to work with branches in forks of the official Eclipse ESCET Git repository in the Eclipse Foundation GitLab, some scripts are provided:

- `misc/fork-collab/fork-checkout-branch.bash <username> <branch_name>`

  Use this script to fetch and checkout the remote branch named `<branch_name>` in the GitLab fork of user `<username>`.

- `misc/fork-collab/fork-push-branch.bash <username> <branch_name>`

  Use this script to push your local changes back to the remote branch named `<branch_name>` in the GitLab fork of user `<username>`. This assumes you have write access to the branch.

Both scripts allow additional arguments to be passed, that are passed on to Git. For instance, pass an extra `-f` to the push script to force push.

If you are not an Eclipse ESCET project committer with write access to our Git repository, see the information on contributing to the Eclipse ESCET project.