Azure DevOps - Pull Request Git "Next steps: Manually resolve these conflicts and push new changes to the source branch."

You will have to do the following on your PC

On branch dev

$ git pull --no-rebase origin master - This will create a merge commit and you will have to resolve the conflicts in the files which are changed both on dev and master. git status will show the list of files with conflicting changes.

After resolving conflicts, commit all the changes and push your branch. After that you should be able to complete the PR.

FYI: --no-rebase makes sure that a merge is done even if the pull behavior is overwritten to default to rebase.

Help link for more details

Since you need to keep the files version on dev branch (keep the source branch while changing files in target branch master), so you should make changes on master branch to resolve the conflict files, and be sure you have permission to push changes to master branch.

You can use below options:

Option 1: merge directly

In your local repo, you can execute below commands to merge dev into master branch while keeping the conflict files version as the dev branch:

git checkout master
git merge dev -X theirs
git push origin master

And in the existing pull request you created, it will shows the branch has been merged. So you can abandon the pull request.

Option 2: still merge via pull request (resolve conflicts on master branch)

You can use below commands to resolve conflicts in master branch:

# In yout local repo
git checkout master
git checkout dev -- .
git commit -m 'replace master branch version by dev for the conflict files'
git push origin master 

While the changes in existing pull request won’t be updated if new commit(s) pushs to the target branch (master). And you can find the similar report Pull request diff does not update when a commit from the PR is merged to the target via another branch.

That means, the pull request in the web page still show the conflicts. You should abandon the existing pull request and reactivate (or create a new one) to merge dev into master branch.