Edit:
I just uploaded an extension that does it:
https://marketplace.visualstudio.com/items?itemName=ShaykiAbramczyk.CreatePullRequest
You can use Azure DevOps Rest API to create a Pull Request, so in the end of the Build / Release add a PowerShell task that do it, for example:
$body = @{
sourceRefName= "$(Build.SourceBranch)"
targetRefName = "refs/heads/master"
title = "PR from Pipeline"
}
$head = @{ Authorization = "Bearer $env:SYSTEM_ACCESSTOKEN" }
$json = ConvertTo-Json $body
$url = "$(System.TeamFoundationCollectionUri)$(System.TeamProject)/_apis/git/repositories/$(Build.Repository.Name)/pullrequests?api-version=5.0"
Invoke-RestMethod -Uri $url -Method Post -Headers $head -Body $json -ContentType application/json
You need to Allow scripts to access the OAuth token (check the checbox in the Agent Job options):
Results:
I put the basic parameters in the body (from branch, to branch, title) but you can add more parameters like reviewers, check the docs here.