Using MR Pre-merging

Introduction

Pre-merging an MR generates a temporary merge node in the repository. When the code in the MR has not been merged, you can download the pre-merge code via plugin scripts such as custom webhooks or pipelines for code building.

Advantages:

• In the MR merging process involving dozens or hundreds of servers for code building, the local client pre-merging result may be different from that generated by the server and yield inaccurate build.
• Enabling MR pre-merge can solve this real-time issue, as the build script commands are simpler compared to local pre-merging scripts, making it easier for developers to get started.

Constraints

• MR pre-merge must be enabled.
• You need to have the set permission. For details, see Configuring Project-Level Permissions.

Example

The following example shows the difference between the scripts with Pre-merge enabled and disabled. The former one is more simple and efficient.

• MR pre-merge enabled: When an MR is created, a temporary merge node will be generated on the server. You can download the code that has been temporarily merged. Steps are provided as follows:

1. Initialize the local repository. In the command, $repo_url indicates the address of the target repository.

   git init  
   git remote add origin ${repo_url}

2. Pulls the temporary merge node from the server to the local branch.

   git fetch origin +refs/merge-requests/${repo_MR_iid}/merge:refs/remotes/origin/${repo_MR_iid}/merge

   • As shown in the following figure, 10 under the merge request title is repo_MR_iid.
     Figure 1 MR IID
     
   • merge-requests/${repo_MR_iid}/merge indicates the temporary merge node.

3. Check out the branch and the pre-merged code is obtained.

   git checkout ${repo_MR_iid}/merge

• MR pre-merge disabled: You need to download the code of the MR source and target branches on the client and merge on your build executor. Steps are provided as follows:

1. Initialize the local repository. In the command, repo_url indicates the address of the target repository.

   git init  
   git remote add origin ${repo_url}

2. Pull and check the target branch of the MR. The repoTargetBranch represents the target branch of the MR.

   git fetch origin +refs/heads/${repoTargetBranch}:refs/remotes/origin/${repoTargetBranch}
   git checkout ${repoTargetBranch}

3. Pull the source branch of the merge request to the local branch.

   git fetch origin +refs/merge-requests/${repo_MR_iid}/head:refs/remotes/origin/${repo_MR_iid}/head

   • As shown in the following figure, 10 under the merge request title is repo_MR_iid.
   Figure 2 MR IID
   
   • merge-requests/${repo_MR_iid}/head indicates the source branch of the merge request.

4. Merge locally and the pre-merged code is generated.

   git merge refs/remotes/origin/${repo_MR_iid}/head --no-edit