# Pipelines for Merged Results
> 原文：[https://docs.gitlab.com/ee/ci/merge_request_pipelines/pipelines_for_merged_results/](https://docs.gitlab.com/ee/ci/merge_request_pipelines/pipelines_for_merged_results/)
* [Prerequisites](#prerequisites)
* [Enable pipelines for merged results](#enable-pipelines-for-merged-results)
* [Using Merge Trains](#using-merge-trains)
* [Automatic pipeline cancellation](#automatic-pipeline-cancellation)
* [Troubleshooting](#troubleshooting)
* [Pipelines for merged results not created even with new change pushed to merge request](#pipelines-for-merged-results-not-created-even-with-new-change-pushed-to-merge-request)
* [Intermittently pipelines fail by `fatal: reference is not a tree:` error](#intermittently-pipelines-fail-by-fatal-reference-is-not-a-tree-error)
# Pipelines for Merged Results[](#pipelines-for-merged-results-premium "Permalink")
[Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/7380) in [GitLab Premium](https://about.gitlab.com/pricing/) 11.10.
提交合并请求时，您正在请求将更改从源分支合并到目标分支. 默认情况下，CI 管道针对源分支运行作业.
使用*用于合并结果*的管道，管道可以像源分支中的更改已被合并到目标分支中一样运行.
如果管道由于目标分支中的问题而失败，则可以等到目标修复后再重新运行管道. 这个新管道将像源与已更新的目标合并一样运行，并且您无需重新设置基准.
目标分支更改时，管道不会自动运行. 仅对源分支的更改会触发新的管道. 如果自上一个成功的管道以来已经过去了很长时间，则您可能需要在合并之前重新运行它，以确保源更改仍然可以成功合并到目标中.
当合并请求无法合并时，管道仅针对源分支运行. 例如，当：
* 目标分支的更改与源分支的更改冲突.
* 合并请求是[**草稿**合并请求](../../../user/project/merge_requests/work_in_progress_merge_requests.html) .
在这些情况下，管道将作为[合并请求](../index.html)的管道运行，并标记为`detached` . 如果这些情况不再存在，则新管道将再次针对合并结果运行.
具有开发者[权限的](../../../user/permissions.html)任何用户都可以运行管道以合并结果.
## Prerequisites[](#prerequisites "Permalink")
要启用管道以合并结果：
* 您必须具有维护者[权限](../../../user/permissions.html) .
* 您必须使用[GitLab Runner](https://gitlab.com/gitlab-org/gitlab-runner) 11.9 或更高版本.
* 您一定不要分叉或使用跨仓库工作流. 要跟踪进度，请参阅[＃11934](https://gitlab.com/gitlab-org/gitlab/-/issues/11934) .
* 您一定不能使用[快速前进合并](../../../user/project/merge_requests/fast_forward_merge.html) . 要跟踪进度，请参阅[＃58226](https://gitlab.com/gitlab-org/gitlab/-/issues/26996) .
## Enable pipelines for merged results[](#enable-pipelines-for-merged-results "Permalink")
要为项目的合并结果启用管道：
1. [配置您的 CI / CD 配置文件，](../index.html#configuring-pipelines-for-merge-requests)以便为合并请求运行管道或单个作业.
2. 访问项目的**设置>常规，**然后展开**合并请求** .
3. Check **为合并结果启用合并训练和管道**.
4. Click **保存更改**.
**警告：**如果选中该复选框，但未将 CI / CD 配置为使用管道处理合并请求，则合并请求可能会停留在未解决的状态，或者管道可能会被丢弃.
## Using Merge Trains[](#using-merge-trains "Permalink")
[为合并结果](#pipelines-for-merged-results-premium)启用[管道时](#pipelines-for-merged-results-premium) ，GitLab 会[自动显示"](merge_trains/index.html#add-a-merge-request-to-a-merge-train) **开始/添加合并训练"按钮** .
通常，这是比立即合并合并请求更安全的选择，因为在实际合并发生之前，将使用预期的合并后结果评估合并请求.
有关更多信息，请阅读[合并火车上](merge_trains/index.html)的[文档](merge_trains/index.html) .
## Automatic pipeline cancellation[](#automatic-pipeline-cancellation "Permalink")
[Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/12996) in [GitLab Premium](https://about.gitlab.com/pricing/) 12.3.
GitLab CI / CD 可以检测到冗余管道的存在，并会自动取消它们以节省 CI 资源.
当用户在进行中的合并列车中立即合并请求时，将重新构建该列车，因为它将重新创建预期的合并后提交和管道. 在这种情况下，合并序列可能已经具有针对先前预期的合并后提交运行的管道. 这些管道被认为是多余的，将被自动取消.
## Troubleshooting[](#troubleshooting "Permalink")
### Pipelines for merged results not created even with new change pushed to merge request[](#pipelines-for-merged-results-not-created-even-with-new-change-pushed-to-merge-request "Permalink")
可能是由于某些禁用的功能标志引起的. 请确保在您的 GitLab 实例上启用了以下功能标志：
* `:merge_ref_auto_sync`
要检查和设置这些功能标志值，请要求管理员：
1. 登录到 GitLab 实例的 Rails 控制台：
```
sudo gitlab-rails console
```
2. 检查标志是否启用：
```
Feature.enabled?(:merge_ref_auto_sync)
```
3. 如果需要，启用功能标志：
```
Feature.enable(:merge_ref_auto_sync)
```
### Intermittently pipelines fail by `fatal: reference is not a tree:` error[](#intermittently-pipelines-fail-by-fatal-reference-is-not-a-tree-error "Permalink")
由于用于合并结果的管道是在合并请求（ `refs/merge-requests/<iid>/merge` ）的合并 ref 上运行的，因此 Git 引用可能会在意外的时间被覆盖. 例如，当源分支或目标分支是高级时. 在这种情况下，流水线由于`fatal: reference is not a tree:`错误而失败，这表明在合并引用中未找到 checkout-SHA.
在 GitLab 12.4 上，通过引入[Persistent pipe refs](../../pipelines/index.html#troubleshooting-fatal-reference-is-not-a-tree)改进了此行为. 您应该能够在任何时候创建管道，而不必考虑错误.
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