Backport action

Fast and flexible GitHub action to backport merged pull requests to selected branches.

This can be useful when you're supporting multiple versions of your product. After fixing a bug, you may want to apply that patch to the other versions. The manual labor of cherry-picking the individual commits can be automated using this action.

Features

• Works out of the box - No configuration required / Defaults for everything
• Fast - Only fetches the bare minimum / Supports shallow clones
• Flexible - Supports all merge methods including merge queue and Bors
• Configurable - Use inputs and outputs to fit it to your project
• Transparent - Informs about its success / Cherry-picks with -x

How it works

You can select the branches to backport merged pull requests in two ways:

• using labels on the merged pull request. The action looks for labels on your merged pull request matching the label_pattern input
• using the target_branches input

For each selected branch, the backport action takes the following steps:

1. fetch and checkout a new branch from the target branch
2. cherry-pick commits containing the merged pull request's changes, using the cherry_picking input
3. create a pull request to merge the new branch into the target branch
4. comment on the original pull request about its success

The commits are cherry-picked with the -x flag.

Usage

Add the following workflow configuration to your repository's .github/workflows folder.

name: Backport merged pull request
on:
  pull_request_target:
    types: [closed]
permissions:
  contents: write # so it can comment
  pull-requests: write # so it can create pull requests
jobs:
  backport:
    name: Backport pull request
    runs-on: ubuntu-latest
    # Only run on merged PRs with a backport label (default `label_pattern`)
    if: >
      github.event.pull_request.merged &&
      contains(toJSON(github.event.pull_request.labels.*.name), '"backport ')
    steps:
      - uses: actions/checkout@v6
      - name: Create backport pull requests
        uses: korthout/backport-action@v4

Note This workflow runs on pull_request_target so that GITHUB_TOKEN has write access to the repo when the merged pull request comes from a forked repository. This write access is necessary for the action to push the commits it cherry-picked.

Trigger using a comment

You can also trigger the backport action by writing a comment containing /backport on a merged pull request. To enable this, add the following workflow configuration to your repository's .github/workflows folder.

name: Backport merged pull request
on:
  pull_request_target:
    types: [closed]
  issue_comment:
    types: [created]
permissions:
  contents: write # so it can comment
  pull-requests: write # so it can create pull requests
jobs:
  backport:
    name: Backport pull request
    runs-on: ubuntu-latest

    # Run on merged PRs with a backport label (default `label_pattern`),
    # or on `/backport` comments.
    if: >
      (
        github.event_name == 'pull_request_target' &&
        github.event.pull_request.merged &&
        contains(toJSON(github.event.pull_request.labels.*.name), '"backport ')
      ) || (
        github.event_name == 'issue_comment' &&
        github.event.issue.pull_request &&
        startsWith(github.event.comment.body, '/backport')
      )
    steps:
      - uses: actions/checkout@v6
      - name: Create backport pull requests
        uses: korthout/backport-action@v4

Determine target branches dynamically

When the default label_pattern can't express your targeting rule, compute target_branches at workflow runtime instead. The target might come from a reviewer's comment, the pull request's base branch, or a config file in the repo.

name: Backport via comment
on:
  issue_comment:
    types: [created]
permissions:
  contents: write # so it can comment
  pull-requests: write # so it can create pull requests
jobs:
  determine-target-branch:
    # Only run on PR comments starting with `/backport ` (note the trailing space — an argument is required).
    if: >
      github.event.issue.pull_request &&
      startsWith(github.event.comment.body, '/backport ')
    runs-on: ubuntu-latest
    outputs:
      branch: ${{ steps.parse-comment.outputs.branch }}
    steps:
      - id: parse-comment
        # Take the first line after `/backport ` as the target branch.
        # The comment body is passed via env to avoid script injection.
        env:
          COMMENT_BODY: ${{ github.event.comment.body }}
        run: |
          branch=$(printf '%s' "$COMMENT_BODY" | head -n1 | sed 's|^/backport ||')
          echo "branch=${branch}" >> "$GITHUB_OUTPUT"

  backport:
    needs: determine-target-branch
    if: needs.determine-target-branch.outputs.branch != ''
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
      - name: Create backport pull requests
        uses: korthout/backport-action@v4
        with:
          target_branches: ${{ needs.determine-target-branch.outputs.branch }}

Signing cherry-picked commits

You may want the cherry-picked commits to be signed, for example to satisfy a protected branch rule, an org policy, or the repo's existing convention.

...
- name: Import GPG key
  id: import-gpg
  uses: crazy-max/ghaction-import-gpg@v6.3.0 # Or any other action to set up GPG
  with:
    gpg_private_key: ${{ secrets.GPG_PRIVATE_KEY }}
    passphrase: ${{ secrets.GPG_PASSPHRASE }}
    git_config_global: true
    git_user_signingkey: true
    git_commit_gpgsign: true
- name: Create backport pull requests
  uses: korthout/backport-action@v4
  with:
    git_committer_name: ${{ steps.import-gpg.outputs.name }}
    git_committer_email: ${{ steps.import-gpg.outputs.email }}

Inputs

The action can be configured with the following optional inputs:

add_author_as_assignee

Default: false (disabled)

Controls whether to set the author of the original pull request as an assignee on the backport pull request. By default, the original author is not made an assignee.

add_author_as_reviewer

Default: false (disabled)

Controls whether to request a review from the author of the original pull request on the backport pull request. By default, the original author is not requested for review.

add_labels

Default: '' (disabled)

The action will add these labels (comma-delimited) to the backport pull request. By default, no labels are added.

add_reviewers

Default: '' (disabled)

The action will add these reviewers (comma-delimited) to the backport pull request. By default, no reviewers are added.

add_team_reviewers

Default: '' (disabled)

The action will add these teams as reviewers (comma-delimited) to the backport pull request. By default, no teams are added.

auto_merge_enabled

Default: false (disabled)

Controls whether to auto-merge the created backport pull request. When enabled, backport pull requests will automatically merge when all required checks pass and approvals are received. Can be set to a simple boolean (true/false) or controlled dynamically via workflow expressions. Examples:

Simple boolean (always enable or disable):

with:
  auto_merge_enabled: true

Opt-in with label (enable auto-merge only when backport-auto-merge label is present):

with:
  auto_merge_enabled: ${{ contains(github.event.pull_request.labels.*.name, 'backport-auto-merge') }}

Opt-out with label (enable auto-merge by default, disable when backport-no-auto-merge label is present):

with:
  auto_merge_enabled: ${{ !contains(github.event.pull_request.labels.*.name, 'backport-no-auto-merge') }}

By default, auto-merge is not enabled.

auto_merge_method

Default: merge

The merge method to use when auto-merge is enabled on backport PRs.

Valid options are:

• merge - Create a merge commit (combines all commits with a merge commit)
• squash - Squash and merge (combines all commits into a single commit)
• rebase - Rebase and merge (replays commits individually without a merge commit)

Important: The specified method must be enabled in your repository's merge settings, otherwise auto-merge will fail.

By default, the backport PR is merged using a merge commit if auto-merge is enabled.

branch_name

Default: backport-${pull_number}-to-${target_branch}

Template used as the name for branches created by this action.

Placeholders can be used to define variable values. These are indicated by a dollar sign and curly braces (${placeholder}). Please refer to this action's README for all available placeholders.

cherry_picking

Default: auto

Determines which commits are cherry-picked.

When set to auto, the action cherry-picks the commits based on the method used to merge the pull request.

• For "Squash and merge", the action cherry-picks the squashed commit.
• For "Rebase and merge", the action cherry-picks the rebased commits.
• For "Merged as a merge commit", the action cherry-picks the commits from the pull request.

When set to pull_request_head, the action cherry-picks the commits from the pull request. Specifically, those reachable from the pull request's head and not reachable from the pull request's base.

By default, the action cherry-picks the commits based on the method used to merge the pull request.

comment_style

Default: legacy

Controls the style of comments posted by the action. When set to legacy, the action posts individual comments per target branch. When set to summary, the action posts a single summary comment per workflow run with actionable details.

copy_all_reviewers

Default: false (disabled)

Controls whether to copy all reviewers from the original pull request to the backport pull request. Note that this requests reviews from both requested reviewers, and people that have already reviewed the original pull request. Use copy_requested_reviewers instead to only request reviews from requested reviewers. By default, all reviewers are not copied.

copy_assignees

Default: false (disabled)

Controls whether to copy the assignees from the original pull request to the backport pull request. By default, the assignees are not copied.

copy_labels_pattern

Default: '' (disabled)

Regex pattern to match github labels which will be copied from the original pull request to the backport pull request. Note that labels matching label_pattern are excluded. By default, no labels are copied.

copy_milestone

Default: false (disabled)

Controls whether to copy the milestone from the original pull request to the backport pull request. By default, the milestone is not copied.

copy_requested_reviewers

Default: false (disabled)

Controls whether to copy the requested reviewers from the original pull request to the backport pull request. Note that this does not request reviews from those users who already reviewed the original pull request. Use copy_all_reviewers instead to also request reviews from those users. By default, the requested reviewers are not copied.

experimental

Default:

{
  "detect_merge_method": false
}

Configure experimental features by passing a JSON object. The following properties can be specified:

conflict_resolution

Default: fail

Specifies how the action will handle a conflict occuring during the cherry-pick. In all cases, the action will stop the cherry-pick at the first conflict encountered.

Behavior is defined by the option selected.

• When set to fail the backport fails when the cherry-pick encounters a conflict.
• When set to draft_commit_conflicts the backport will always create a draft pull request with the first conflict encountered committed.

Instructions are provided on the original pull request on how to resolve the conflict and continue the cherry-pick.

downstream_repo

Define if you want to backport to a repository other than where the workflow runs.

By default, the action always backports to the repository in which the workflow runs.

downstream_owner

Define if you want to backport to another owner than the owner of the repository the workflow runs on. Only takes effect if the downstream_repo property is also defined.

By default, uses the owner of the repository in which the workflow runs.

github_token

Default: ${{ github.token }}

Token to authenticate requests to GitHub. Used to create and label pull requests and to comment.

Either GITHUB_TOKEN or a repo-scoped Personal Access Token (PAT).

github_workspace

Default: ${{ github.workspace }}

Working directory for the backport action.

git_committer_name

Default: github-actions[bot]

Name of the committer for the cherry-picked commit.

git_committer_email

Default: github-actions[bot]@users.noreply.github.com

Email of the committer for the cherry-picked commit.

label_pattern

Default: ^backport ([^ ]+)$ (e.g. matches backport release-3.4)

Regex pattern to match the backport labels on the merged pull request. Must contain a capture group for the target branch. Label matching can be disabled entirely using an empty string '' as pattern.

The action will backport the pull request to each matched target branch. Note that the pull request's headref is excluded automatically. See How it works.

merge_commits

Default: fail

Specifies how the action should deal with merge commits on the merged pull request.

• When set to fail the backport fails when the action detects one or more merge commits.
• When set to skip the action only cherry-picks non-merge commits, i.e. it ignores merge commits. This can be useful when you keep your pull requests in sync with the base branch using merge commits.

pull_description

Default:

# Description
Backport of #${pull_number} to `${target_branch}`.

Template used as description (i.e. body) in the pull requests created by this action.

Placeholders can be used to define variable values. These are indicated by a dollar sign and curly braces (${placeholder}). Please refer to this action's README for all available placeholders.

pull_title

Default: [Backport ${target_branch}] ${pull_title}

Template used as the title in the pull requests created by this action.

Placeholders can be used to define variable values. These are indicated by a dollar sign and curly braces (${placeholder}). Please refer to this action's README for all available placeholders.

source_pr_number

Default: '' (not set)

Specifies the pull request (by its number) to backport, i.e. the source pull request. When set, the action will backport the specified pull request to each target branch. When not set, the action determines the source pull request from the event payload.

target_branches

Default: '' (disabled)

The action will backport the pull request to each specified target branch (space-delimited). Note that the pull request's headref is excluded automatically. See How it works.

Can be used on its own (no labels required) or alongside backport labels — when both are set, the action backports to the union of the two. By default, only backport labels are used to specify the target branches.

See also Determine target branches dynamically for computing this input at workflow runtime.

Placeholders

In the pull_description and pull_title inputs, placeholders can be used to define variable values. These are indicated by a dollar sign and curly braces (${placeholder}). The following placeholders are available and are replaced with:

Outputs

The action provides the following outputs: