Azure DevOps Merge Conflicts Prevention and Resolution

Merge conflicts can be a real pain in Azure DevOps, but there are ways to prevent and resolve them. Azure DevOps provides a feature called "Branch Policies" that can help prevent merge conflicts by enforcing certain rules on branches.

A simple rule, such as requiring a pull request to be approved before it can be merged, can greatly reduce the likelihood of conflicts. By doing so, you can catch potential issues before they become a problem.

Azure DevOps also provides a feature called "Merge Queue" that allows you to review and resolve merge conflicts before they are committed to the main branch. This feature can be a huge time-saver and reduce the stress of dealing with conflicts.

To prevent merge conflicts in Azure DevOps, be aware of the situations where rebasing during PR completion isn't possible. If a policy on the target branch prohibits using rebase strategies, you need Override branch policies permission to rebase.

You can't rebase a PR source branch if it has policies, as rebasing would modify the source branch without going through the policy approval process.

If you've used the Merge Conflict Extension to resolve merge conflicts, rebasing isn't an option because conflict resolutions applied to a three-way merge are seldom successful or valid when rebasing all the PR commits individually.

In these cases, you can still rebase your branch locally and then push upstream, or squash-merge your changes when you complete the PR.

Here are the scenarios where rebasing during PR completion isn't possible:

Conflicts in Azure DevOps can be frustrating, but understanding how they work can help you resolve them more easily.

A fast-forward merge can never have a conflict because Git won't apply a fast-forward merge if the tip of the target branch has diverged from the source branch.

If you do encounter a conflict, you'll need to resolve it to complete the merge or rebase. This can be done by manually correcting the conflicts in the bottom pane, or by picking the entire left or right side.

Git rebase resequences the commit history of the target branch so that it contains all source branch commits, followed by all target branch commits since the last common commit.

In some cases, you may see a warning message "Multiple merge base detected. The list of commits displayed might be incomplete." This can be resolved by rebasing and then force pushing, but it's worth noting that merge is normally preferred over rebase.

There are extensions available, such as the Pull Request Merge Conflict Extension, which can help you resolve conflicts inside the pull request page.

Managing conflict issues is a crucial part of the Azure DevOps merge process. Multiple merge base issues can cause security issues if files in a PR have different versions between merge bases.

A fast-forward merge can never have a merge conflict because Git won't apply a fast-forward merge if the tip of the target branch has diverged from the source branch.

To resolve merge conflicts, you must resolve any merge conflicts between the PR branch and the target branch before you can merge a PR or set the PR to autocomplete.

Reviewing branch policies is a crucial step in managing conflict issues in your codebase. You can set branch policies that require PRs in protected branches to meet specific criteria before they can merge.

Teams can see the branch policies in effect for their PR, including whether they're required for merge and whether the PR is passing or failing. The PR Overview tab summarizes branch policies that are passing or failing for the PR.

Branch policy requirements have an icon on the PR Overview page. Selecting More options next to the requirement and then selecting View policy takes you to the branch's Branch Policies page in Project Settings.

You can also use the command az repos pr policy list with the required id parameter to see all branch policies that are in effect for a PR.

Multiple merge base issue can cause security issues if the files in a PR have different versions between the merge bases.

A multiple merge base warning happens in such situations, and for more information and remediation, see Multiple merge bases.

File changes in your branch can conflict with changes in another branch, and Git shows the files that conflict on the PR's Overview page.

You must resolve any merge conflicts between the PR branch and the target branch before you can merge a PR or set the PR to autocomplete.

Resolve merge conflicts by following the instructions provided, and it's essential to resolve merge conflicts to complete the merge or rebase operation.

A fast-forward merge can never have a merge conflict because Git won't apply a fast-forward merge if the tip of the target branch has diverged from the source branch.