Git Backporting
📤 📥

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Git Backporting is a NodeJS command line tool that provides capabilities to backport pull requests (on GitHub) and merge requests (on GitLab) in an automated way. This tool also comes with a predefined GitHub action in order to make CI/CD integration easier for all users.

Table of content

• Who is this tool for
• CLI tool
• GitHub action
• Future works
• Development
• Contributing
• License

Who is this tool for?

git-backporting is a fully configurable tool that provides capabilities to backport pull requests (on GitHub) and merge requests (on GitLab) in an automated way.

What is backporting? - backporting is an action aiming to move a change (usually a commit) from a branch (usually the main one) to another one, which is generally referring to a still maintained release branch. Keeping it simple: it is about to move a specific change or a set of them from one branch to another.

Therefore this tools is for anybody who is working on projects where they have to maintain multiple active branches/versions at the same time. If you are actively cherry-picking many changes from your main branch to other ones, and you mainly do changes through pull requests or merge requests, maybe this tool may be right for you.

CLI tool

All instructions provided below pertain to version v4 of the tool. If you wish to use an earlier version, please refer to the documentation from the corresponding tag/release.

This tool is released on the public npm registry, therefore it can be easily installed using npm:

$ npm install -g @kie/git-backporting

Then you just have to choose the pull request (or merge request on Gitlab) that you would like to backport and the target branch and then simply run the following command:

$ git-backporting -tb <branch> -pr <pull-request-url> -a <git-token>

A real example could be the following one:

$ git-backporting -tb develop -pr https://github.com/kiegroup/git-backporting-example/pull/47 -a *****

This is the easiest invocation where you let the tool set / compute most of the backported pull request data. Obviously most of that data can be overridden with appropriate tool options, more details can be found in the inputs section.

Requirements

• Node 16 or higher, more details on Node can be found here.
• Git, see how to install if you need help.

How it works?

It works in this way: given the provided pull/merge request it infers the server API to use (either Github or Gitlab for now) and retrieves the corresponding pull request object (original pull/merge request to be backported into another branch).

After that it clones the corresponding git repository, check out in the provided target branch and create a new branch from that (name automatically generated if not provided as option).

By default the tool will try to cherry-pick the single squashed/merged commit into the newly created branch. The --no-squash and --auto-no-squash options control this behavior according the following table.

No squash	Auto no squash	Behavior
unset/false	unset/false	cherry-pick a single commit, squashed or merged
set/true	unset/false	cherry-pick all commits found in the the original pull/merge request
(ignored)	set/true	cherry-pick all commits if the original pull/merge request was merged, a single commit if it was squashed

Based on the original pull request, creates a new one containing the backporting to the target branch. Note that most of these information can be overridden with appropriate CLI options or GHA inputs.

cherry-pick strategy

The default cherry-pick strategy is recursive with theirs option for automatic conflicts resolution. Therefore, by default, all commits are cherry-picked using the following git-equivalent command:

$ git cherry-pick -m 1 --strategy=recursive --strategy-option=theirs <sha>

From version v4.2.0 both can be configured via the strategy or strategy-option inputs if using the action and the --strategy or --strategy-option arguments if using the CLI.

The default strategy of the git-cherry-pick command is different from the defaults of git-backporting.

$ git cherry-pick -m 1 <sha>

is the same as:

$ git cherry-pick -m 1 --strategy=ort --strategy-option=find-renames <sha>

If there is a conflict the backport will fail and require manual intervention.

NOTE: If there are any conflicts, the tool will block the process and exit signalling the failure as there are still no ways to interactively resolve them. In these cases a manual cherry-pick is needed, or alternatively users could manually resume the process in the cloned repository (here the user will have to resolve the conflicts, push the branch and create the pull request - all manually).

Inputs

This tool comes with some inputs that allow users to override the default behavior, here the full list of available inputs:

Name	Command	Required	Description	Default
Version	-V, --version	-	Current version of the tool
Help	-h, --help	-	Display the help message
Target Branches	-tb, --target-branch	N	Comma separated list of branches where the changes must be backported to
Target Branches Pattern	-tbp, --target-branch-pattern	N	Regular expression pattern to extract target branch(es) from pr labels. The branches will be extracted from the pattern's required target named capturing group, e.g., ^backport (?<target>([^ ]+))$
Pull Request	-pr, --pull-request	N	Original pull request url, the one that must be backported, e.g., #1
Configuration File	-cf, --config-file	N	Configuration file, in JSON format, containing all options to be overridded, note that if provided all other CLI options will be ignored
Auth	-a, --auth	N	Git access/authorization token, if provided all token env variables will be ignored. See auth token section for more details	""
Folder	-f, --folder	N	Local folder full name of the repository that will be checked out, e.g., /tmp/folder	{cwd}/bp
Git Client	--git-client	N	Git client type <github	gitlab
Git User	-gu, --git-user	N	Local git user name	"GitHub"
Git Email	-ge, --git-email	N	Local git user email	"noreply@github.com"
Title	--title	N	Backporting pull request title	"{original-pr-title}"
Body	--body	N	Backporting pull request body	"{original-pr-body}"
Body Prefix	--body-prefix	N	Prefix to the backporting pull request body	"Backport: {original-pr-link}"
Reviewers	--reviewers	N	Backporting pull request comma-separated reviewers list	[]
Assignees	--assignes	N	Backporting pull request comma-separated assignees list	[]
No Reviewers Inheritance	--no-inherit-reviewers	N	Considered only if reviewers is empty, if true keep reviewers as empty list, otherwise inherit from original pull request	false
Backport Branch Names	--bp-branch-name	N	Comma separated lists of the backporting pull request branch names, if they exceeds 250 chars they will be truncated	bp-{target-branch}-{sha1}...{shaN}
Labels	--labels	N	Provide custom labels to be added to the backporting pull request	[]
Inherit labels	--inherit-labels	N	If enabled inherit lables from the original pull request	false
No squash	--no-squash	N	Backport all commits found in the pull request. The default behavior is to only backport the first commit that was merged in the base branch.
Auto no squash	--auto-no-squash	N	If the pull request was merged or is open, backport all commits. If the pull request commits were squashed, backport the squashed commit.
Strategy	--strategy	N	Cherry pick merging strategy, see git-merge doc for all possible values	"recursive"
Strategy Option	--strategy-option	N	Cherry pick merging strategy option, see git-merge doc for all possible values	"theirs"
Cherry-pick Options	--cherry-pick-options	N	Additional cherry-pick options, see git-cherry-pick doc for all possible values	"theirs"
Additional comments	--comments	N	Semicolon separated list of additional comments to be posted to the backported pull request	[]
Enable error notification	--enable-err-notification	N	If true, enable the error notification as comment on the original pull request	false
Dry Run	-d, --dry-run	N	If enabled the tool does not push nor create anything remotely, use this to skip PR creation	false

NOTE: pull request and (target branch or target branch pattern) are mandatory, they must be provided as CLI options or as part of the configuration file (if used).

Authorization token

Since version 4.5.0 we introduced a new feature that allows user to provide the git access token through environment variables. These env variables are taken into consideration only if the --auth/-a is not provided as argument/input. Here the supported list of env variables:

• GITHUB_TOKEN: this is checked only if backporting on Github platform.
• GITLAB_TOKEN: this is checked only if backporting on Gitlab platform.
• CODEBERG_TOKEN: this is checked only if backporting on Codeberg platform.
• GIT_TOKEN: this is considered if none of the previous envs are set.

NOTE: if --auth argument is provided, all env variables will be ignored even if not empty.

Configuration file example

This is an example of a configuration file that can be used.

{
  "pullRequest": "https://gitlab.com/<namespace>/<repo>/-/merge_requests/1",
  "targetBranch": "old",
  "folder": "/tmp/my-folder",
  "title": "Override Title",
  "auth": "*****"
}

Keep in mind that its structure MUST match the Args interface, which is actually a camel-case version of the CLI options.

Supported git services

Right now Git Backporting supports the following git management services:

• GITHUB: Introduced since the first release of this tool (version 1.0.0). The interaction with this system is performed using octokit client library.

• GITLAB: This has been introduced since version 3.0.0, it works for both public and private GitLab servers. The interaction with this service is performed using plain axios requests. The gitlab api version that is used to make requests is v4, at the moment there is no possibility to override it.

• CODEBERG: Introduced since version 4.4.0, it works for public codeberg.org platform. Thanks to the api compatibility with GitHub, the interaction with this service is performed using using octokit client library.

NOTE: by default, all gitlab requests are performed setting rejectUnauthorized=false, planning to make this configurable too.

GitHub action

This action can be used in any GitHub workflow, below you can find a simple example of manually triggered workflow backporting a specific pull request (provided as input).

name: Pull Request Backporting using Git Backporting

on: 
  workflow_dispatch:
    inputs:
      targetBranch:
        description: 'Target branch'
        required: true
        type: string
      pullRequest:
        description: 'Pull request'
        required: true 
        type: string
      dryRun:
        description: 'Dry run'
        required: false
        default: "true" 
        type: string

jobs:
  backporting:
    name: "Backporting"
    runs-on: ubuntu-latest
    steps:
      - name: Backporting
        uses: kiegroup/git-backporting@main
        with:
          target-branch: ${{ inputs.targetBranch }}
          pull-request: ${{ inputs.pullRequest }}
          auth: ${{ secrets.GITHUB_TOKEN }}
          dry-run: ${{ inputs.dryRun }}

You can also use this action with other events - you'll just need to specify target-branch and pull-request params.

For example, this configuration creates a pull request against branch v1 once the current one is merged, provided that the label backport-v1 is applied:

name: Pull Request Backporting using Git Backporting

on:
  pull_request_target:
    types:
      - closed
      - labeled

env:
  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

jobs:
  backporting:
    name: "Backporting"
    # Only react to merged PRs for security reasons.
    # See https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request_target.
    if: >
      github.event.pull_request.merged
      && (
        github.event.action == 'closed'
          && contains(github.event.pull_request.labels.*.name, 'backport-v1')
        || (
          github.event.action == 'labeled'
          && contains(github.event.label.name, 'backport-v1')
        )
      )
    runs-on: ubuntu-latest
    steps:
      - name: Backporting
        uses: kiegroup/git-backporting@main
        with:
          target-branch: v1
          pull-request: ${{ github.event.pull_request.url }}

For a complete description of all inputs see Inputs section.

Future works

Git Backporting is still in development mode, this means that there are still many future works and extension that can be implemented. I'll try to summarize the most important ones:

• Provide a way to backport single commit (or a set of them) if no original pull request is present.
• Integrate this tool with other git management services (like Bitbucket) to make it as generic as possible.
• Integrate it into other CI/CD services like gitlab CI.
• Provide some reusable GitHub workflows.

Development

Package release

The release of this package is entirely based on release-it tool. I created some useful scripts that can make the release itself quite easy.

Automatic release

The first step is to prepare the changes for the next release, this is done by running:

$ npm run release:prepare:all

NOTE: running locally this requires npm login, please consider using .github/workflows/prepare-release.yml if you don't have permission on the npm package.

This script performs the following steps:

1. Automatically computes the next version based on the last commits
2. Create a new branch release/v${computed_version}
3. Apply all changes, like version and changelog upgrade
4. Commit those changes: chore: release v${compute_version}

After that you should just push the new branch and open the pull request.

NOTE: if you don't want to run this preparation from you local environment, there is already a workflow that does all these steps, including the pull request. See Prepare release workflow.

Once the release preparion pull request got merged, you can run Release package workflow that automatically performs the release itself, including npm publishing, git tag and github release.

Manual release

In case we would like to perform a manual release, it would be enough to open a pull request changing the following items:

• Package version inside the package.json
• Provide exhaustive changelog information inside CHANGELOG.md
• Commit like chore: release v<version>

Once the release preparion pull request got merged, run Release package workflow.

Contributing

This is an open source project, and you are more than welcome to contribute ❤️!

Every change must be submitted through a GitHub pull request (PR). Backporting uses continuous integration (CI). The CI runs checks against your branch after you submit the PR to ensure that your PR doesn’t introduce errors. If the CI identifies a potential problem, our friendly PR maintainers will help you resolve it.

Note: this project follows git-conventional-commits standards, thanks to the commit-msg hook you are not allowed to use commits that do not follow those standards.

1. Fork it (https://github.com/kiegroup/git-backporting).

2. Create your feature branch: (git checkout -b feature).

3. Commit your changes with a comment: (git commit -am 'Add some feature').

4. Push to the branch to GitHub: (git push origin feature).

5. Create a new pull request against main branch.

Note: you don't need to take care about typescript compilation and minifycation, there are automated git hooks taking care of that!

Hint: if you are still in a work in progress branch and you want to push your changes remotely, consider adding --no-verify for both commit and push, e.g., git push origin <feat-branch> --no-verify

License

Git backporting open source project is licensed under the MIT license.