Navigating Feature Deployment with Git: A Guide
Tags: git, versioncontrol, deployment, softwareengineering
Published: 2024-03-31 06:49:27

Deploying software features can sometimes require selective inclusion, especially in scenarios where multiple features have been developed concurrently but only a subset is ready or chosen for release. Let's explore a practical scenario: Person A and Person B have each developed a feature, both of which are now merged into the `develop` branch. However, only the feature developed by Person A is slated for deployment. How do we handle this situation effectively using Git? This post will guide you through the correct approach to ensure a smooth and error-free deployment process.

#### Understanding the Challenge

First, it's crucial to understand the challenge at hand. Merging both features into the `develop` branch means they are both part of the upcoming release candidate. However, with the decision to deploy only Person A's feature, we need to find a way to exclude Person B's changes temporarily without losing the work done.

#### The Correct Git Strategy

The best approach involves using Git's powerful branch management and manipulation features. Here's a step-by-step guide:

1. **Create a Release Branch:** Start by creating a new branch from the `develop` branch. This branch will be your release branch, where you'll prepare the code that is actually going to be deployed. For example:
    ```git
    git checkout develop
    git pull origin develop
    git checkout -b release/your-feature-release
    ```

2. **Revert Unwanted Features:** Since both features are already merged, the next step is to exclude Person B's feature from this release. This can be achieved by using the `git revert` command. The revert operation will create a new commit on top of the current branch that undoes the changes introduced by Person B's feature merge commit.
   
    Identify the merge commit of Person B's feature and revert it:
    ```git
    git revert -m 1 <merge-commit-hash>
    ```
    The `-m 1` option specifies which parent of the merge commit you want to keep, which, in most cases, is the main branch (`develop` branch in this case) from which the feature was merged.

3. **Test the Release Branch:** Before proceeding to deploy, it's crucial to thoroughly test the release branch to ensure that reverting Person B's feature hasn't introduced any unforeseen issues and that Person A's feature is working as expected.

4. **Deploy the Release Branch:** Once testing confirms everything is in order, the release branch is ready to be deployed to production.

5. **Re-integrate the Release Branch:** After successful deployment, don't forget to merge the release branch back into the `develop` branch. This ensures that the revert of Person B's feature is also reflected in the `develop` branch, maintaining consistency. Person B's feature can then be reintroduced or merged again when it's ready for deployment in a future release.
    ```git
    git checkout develop
    git merge release/your-feature-release
    git push origin develop
    ```

#### Additional Insights on the `git revert -m 1 <merge-commit-hash>` Command

The `git revert` command is an incredibly useful tool in Git for effectively undoing changes from a specific commit. When faced with a scenario where you need to reverse the changes introduced by a merge commit, adding the `-m 1` option to the `git revert` command plays a crucial role.

**Understanding Merge Commits:**
Merge commits occur when two or more branches are merged together, resulting in a commit with more than one parent. This complexity is why the `-m` option is needed.

**Meaning of `-m 1`:**
The `-m` option stands for "mainline" and is followed by a number indicating which parent branch of the merge commit should be considered the mainline for the revert. Using `-m 1` tells Git to treat the first parent as the mainline, effectively reverting the changes introduced by merging the second branch into the first.

**Why Use `-m 1`?**
This option is particularly useful when you want to revert a feature merged into a main branch like `develop` or `master` without affecting the overall project history. It allows for selective reversion of specific features, making it an essential command for managing complex deployment scenarios.

**Practical Example:**
If you merged a `feature-b` branch into `develop` and later decide to revert the changes introduced by `feature-b`, you would locate the merge commit hash and then run:
```git
git revert -m 1 <merge-commit-hash>
```
This command creates a new commit on top of `develop` that reverses the changes made by merging `feature-b`, effectively rolling back the branch to its state before the merge, without discarding the entire history of changes.

#### Conclusion

This strategy enables teams to selectively deploy features while maintaining the integrity of the development process and ensuring that no work is lost. It showcases the flexibility and power of Git as a tool for managing complex development workflows. By carefully managing branches and utilizing the revert functionality, teams can adapt to changing requirements and ensure that only the ready and approved features make it to production, demonstrating the practical application of the `git revert -m 1 <merge-commit-hash>` command in real-world scenarios.