Improve the error messages

[korthout]

Is your feature request related to a problem? Please describe.
Most comments by the action for errors are unclear, unhelpful, and appear to come from nowhere.

Example no permission to push to repo:

Git push to origin failed for case5-backport-target with exitcode 1

Describe the solution you'd like
Error messages should be clear about what was attempted, what went wrong, and what can be done to recover. For example:

Backport-action failed to generate a pull request cherry-picking these changes (workflow run). Tried to push branch backport-x-to-y, but not permitted to push to this repo.

You can use a Personal Access Token (PAT) with repo scope as the token input of the actions/checkout-action step to permit pushing to the repo.

Describe alternatives you've considered
..

Additional context
Some other example errors:

Not permitted to create pull request:

Resource not accessible by integration

Unable to cherry-pick

This error is clear about what happened, what went wrong, and how to recover. However, it still appears to come out of nowhere. A link to the workflow run would help.

Backport failed for stable/8.2, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin stable/8.2
git worktree add -d .worktree/backport-16634-to-stable/8.2 origin/stable/8.2
cd .worktree/backport-16634-to-stable/8.2
git switch --create backport-16634-to-stable/8.2
git cherry-pick -x a472372cdb055835682b13515442139655126034 02910366c2d4aff900c41a4dfd8de1f0e926dfae

[ggwpez]

I have this problem as well, where the bot just comments that something went wrong after i successfully merged the backport. To me it looks like everything went well:

[ggwpez]

PS: It is probably of how am using target_branches. In our repo we dont really want the developer to having to specify all the branches that they should backport in.
But specifying a label filter and target_branches at the same time seems to still try and backport even the backports again - which fails.

Could it be possible to have labels that dont require a regex matchgroup but rather only serve as a tag to trigger for all target_branches?

[korthout]

@ggwpez It looks like your workflow is trying to backport the changes a second time. The merged PR's base to backport is the same as the selected target branch. This may lead to conflicts during cherry-picking, which explains why you'd see this error.

That's a bug, as backport-action could always exclude this unique case. There's no reason to port changes that were just merged to a branch again to that same branch. To verify that this happened, I'd be interested to see the workflow run logs, particularly the lines regarding:

Determining target branches..

While we should eventually resolve that as a separate bug, you could work around this by excluding PRs that directly target your target branch.

Something like:

    # Only backport to my_target_branch, if PR did not just merge something to it
    if: >
      github.event.pull_request.merged &&
      github.event.pull_request.base.ref != 'my_target_branch'
    steps:
      - uses: actions/checkout@v4
      - uses: korthout/backport-action@v3
        with:
          target_branches: my_target_branch

Could it be possible to have labels that dont require a regex matchgroup but rather only serve as a tag to trigger for all target_branches?

You could also try this. You can use a similar condition checking for specific labels. It may be useful to split up the different usages into separate workflows then:

• one workflow to backport using a label with capture group when that's needed
• one workflow to backport to a specific branch/branches when a specific label is used

Hope it helps, and let me know if you run into issues. Feel free to open a bug if you encounter new issues.

[ggwpez]

Thanks for taking a look, your workaround with excluding the base.ref works. It seems to indeed end up with an empty commit while trying to backport the backport. I did not realize that it is using the workflow file from the stable branch instead of master. Full error log:

Details

Run korthout/backport-action@v3
  with:
    target_branches: stable[2](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:2)407
    merge_commits: skip
    github_token: ***
    label_pattern: A4-needs-backport
    pull_description: Backport #${pull_number} into `${target_branch}` (cc @${pull_author}).
  
    pull_title: [${target_branch}] Backport #${pull_number}
  
    branch_name: backport-${pull_number}-to-${target_branch}
    cherry_picking: auto
    copy_assignees: false
    copy_milestone: false
    copy_requested_reviewers: false
    experimental: {
    "conflict_resolution": "fail"
  }
  
    github_workspace: /home/runner/work/debug/debug
Retrieve pull request data for #85
Check whether pull request 85 is merged
Determining target branches...
Detected labels on PR: A[3](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:3)-backport
label 'A3-backport' doesn't match `label_pattern` 'A[4](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:4)-needs-backport'
Found target branches in labels: 
Found target branches in `target_branches` input: stable2407
Exclude pull request's headref from target branches: backport-84-to-stable2407
Determined target branches: stable2407
Fetching all the commits from the pull request: 2
git fetch --depth=2 origin refs/pull/8[5](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:5)/head
From https://github.com/ggwpez/debug
 * branch            refs/pull/85/head -> FETCH_HEAD
Retrieving the commits from pull request 85
PR was merged using a squash or a rebase. Choosing squash strategy.
git fetch --depth=2 origin +1[6](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:6)4f1c6a4799a307be59dfc2ae9c298995a1e133:refs/remotes/origin/164f1c6a4[7](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:7)99a307be59dfc2ae9c298995a1e133
From https://github.com/ggwpez/debug
 * [new ref]         164f1c6a4799a307be59dfc2ae9c29[8](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:8)[9](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:9)95a1e133 -> origin/164f1c6a4799a307be59dfc2ae9c298995a1e133
Found commits to backport: 164f1c6a4799a307be59dfc2ae9c298995a1e133
Checking the merged pull request for merge commits
git rev-list --merges 164f1c6a4799a307be59dfc2ae9c298995a1e[13](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:13)3^..164f1c6a4799a307be59dfc2ae9c298995a1e133
Encountered 0 merge commits
Will cherry-pick the following commits: [16](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:16)4f1c6a4799a307be59dfc2ae9c298995a1e133
Will copy labels matching undefined. Found matching labels: 
Backporting to target branch 'stable2407...'
git fetch --depth=1 origin stable2407
From https://github.com/ggwpez/debug
 * branch            stable[24](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:25)07 -> FETCH_HEAD
Start backport to backport-85-to-stable2407
git switch -c backport-85-to-stable2407 origin/stable2407
Switched to a new branch 'backport-85-to-stable2407'
git cherry-pick -x 164f1c6a4799a307be59dfc2ae9c298995a1e133
The previous cherry-pick is now empty, possibly due to conflict resolution.
If you wish to commit it anyway, use:

    git commit --allow-empty

Otherwise, please use 'git cherry-pick --skip'
git cherry-pick --abort
Backport failed for `stable2407`, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.
``bash
git fetch origin stable2407
git worktree add -d .worktree/backport-85-to-stable2407 origin/stable2407
cd .worktree/backport-85-to-stable2407
git switch --create backport-85-to-stable2407
git cherry-pick -x 164f1c6a4799a307be59dfc2ae9c[29](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:30)8995a1e133
``
Create comment: Backport failed for `stable2407`, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.
``bash
git fetch origin stable2407
git worktree add -d .worktree/backport-85-to-stable2407 origin/stable2407
cd .worktree/backport-85-to-stable2407
git switch --create backport-85-to-stable2407
git cherry-pick -x 164f1c6a4799a[30](https://github.com/ggwpez/debug/actions/runs/10595239845/job/29360562571#step:3:31)7be59dfc2ae9c298995a1e133
``

For future readers, this is the workflow that am currently using:

Details

name: Backport into stable

on:
  pull_request_target:
    types: [ closed, labeled ]
  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

    # Excluding CI action user id `97796249`:
    if: >
      ( !startsWith(github.event.pull_request.base.ref, 'stable') ) &&
      ((
        github.event_name == 'pull_request_target' &&
        github.event.pull_request.merged &&
        contains(github.event.pull_request.labels.*.name, 'A4-needs-backport')
      ) || (
        github.event_name == 'issue_comment' &&
        github.event.issue.pull_request &&
        github.event.comment.user.id != 97796249 &&
        (
          startsWith(github.event.comment.body, '/backport') ||
          contains(toJson(github.event.comment.body), '\n/backport')
        )
      ))
    steps:
      - uses: actions/checkout@v4
      - name: Create backport pull requests
        uses: korthout/backport-action@v3
        id: backport
        with:
          target_branches: stable2407 stable2410
          merge_commits: skip
          github_token: ${{ secrets.GITHUB_TOKEN }}
          pull_description: |
            Backport #${pull_number} into `${target_branch}` (cc @${pull_author}).

            <!--
              # To be used by other automation, do not modify:
              original-pr-number: #${pull_number}
            -->
          pull_title: |
            [${target_branch}] Backport #${pull_number}

      - if: ${{ steps.backport.outputs.created_pull_numbers != '' }}
        uses: actions/github-script@v7
        with:
          script: |
            const pullNumbers = '${{ steps.backport.outputs.created_pull_numbers }}'.split(' ');
            
            for (const pullNumber of pullNumbers) {
              await github.rest.issues.addLabels({
                issue_number: parseInt(pullNumber),
                owner: context.repo.owner,
                repo: context.repo.repo,
                labels: ['A3-backport']
              });
              console.log(`Added A3-backport label to PR #${pullNumber}`);
            }