So you’re evolving your source control practice. You have created a ‘dev’ branch to keep work in progress away from the ‘main’ branch, and maybe you are even using feature branches or branches per developer. As you are putting in place branch policies to prevent just anybody from committing changes, you notice a pattern of commits being created just by merging a change into ‘main’. In this post I will show you how to limit the number of commits.
I have a simple project in Azure DevOps, with a repo that has a default branch called ‘main’ and a ‘dev’ branch. The main branch requires a reviewer, which in Azure DevOps means that changes can only be made through pull requests. I’ve committed a couple of changes in dev and I have created a pull request to move that change into the main branch to be released. The PR has been approved and I have clicked the ‘Complete’ button on the PR. The Azure DevOps default Merge Type is set to ‘Merge’ and all looks well, so then I click the ‘Complete Merge’ button.
When the PR completes, you go back to the Branches view in Azure DevOps, and you notice that the dev branch is 1 commit behind on Main….
Wait, what? Didn’t I just merge 2 commits from dev into Main? The purpose of the PR was to synchronize the branches, but it appears that dev now a commit behind main. The Merge Type of ‘Merge’ created its own commit in the target branch, main in this case. When you go back to VSCode and merge main back into dev, you would notice that the source files themselves have not changed, even though Git has created two extra commits just from the Merge actions. You see, any time that you do a Merge in Git, it will generate a new commit.
If you were to do a file compare between the two branches, there would be no differences in the source files. The not so good part of using the Merge Type ‘Merge’ is that you will have to refresh your local main branch and merge that into your dev branch BEFORE you can continue developing. In itself maybe this works for many people but I prefer it if I can push out my dev work and continue developing without having to worry about being in synch with main.
A Better Way
There is another (I would argue a ‘better’) way to complete PRs. Another setup: I’ve updated my local main and merged that into my local dev branch; I have made another code change, which I have pushed that to the remote from my VSCode. The Branches view in Azure DevOps now shows dev is one commit ahead of main.
This time when you complete the PR, you select ‘Rebase and fast-forward’ as the Merge Type.
Because we are not merging, Git will not create a new commit. The result of this Merge Type is that the branches are in synch after completing the PR. There is no need for me to go back to VSCode and update my main branch.
So What is the Difference?
I’ll be totally honest here and tell you that I don’t really understand the difference between ‘Merge’ and ‘Rebase’. Something about where in the first the differences are actually merged and the changes are preserved in a new commit, and in the second the branch is rebased and the incoming changes are applied to that new base. I am sure that there is a distinct difference, and that this has an impact on the way you manage branches. I’ve looked for but could not find any posts that clearly explain the two with proper examples. I’m still looking, and I still want to know, but I have other more important things to worry about right now. Maybe a good topic to write about in the future :).
For practical purposes though, for the type of projects that I am involved in, I prefer the Rebase option. Personally, I prefer the branches to be synchronized when a PR is completed. Having to go back and pull the merge commit back into my local dev branch feels like a redundant step.