How can you programmatically raise a conditional PR? - azure-devops

Question

We currently have the following branch strategy:
Develop > Release > Master
Devs create a local branch from Develop, make changes merge to develop. Our dev environment builds off that branch. When they want their changes tested they push to QA environment, which also uses the Develop branch. This cycle goes on until functional testing for the iteration is done. At that point the code is merged into the Release branch and is deployed through staging and then to prod. After deploying to prod the code should be merged to Master, but it's often forgotten about. This causes problems in niche scenarios.
Is there a way to use perhaps devops pipelines to conditionally raise a PR automatically? So I'm thinking this would need 2 PRs:
PR raised for Master branch after successful release to prod. Idea here would be once sign off has been granted someone from the team can just approve.
PR raised for Develop branch if the first PR is approved and the code in Master now differs from Develop. In a lot of cases it won't as therefore wouldn't need a PR.
I've been googling for this and found the api methods like this but I can't see how you could put this in a pipeline and make it conditional.
Additional Info:
My understanding is that the build definition needs to know what branch to build as per the image below. So, creating a new release branch every sprint would either result in having to update the build definition every time or creating a new build definition, that essentially would be a complete replica in most cases except for the branch name. Unless I'm misunderstanding, which I think I am.

Answer 1

The following PowerShell example creates a pull request from master to some target branch as a build task. You can add it to your release as an additional stage "Create PR to some branch" with one PowerShell task. Additionally, you can create periodically build to check diff and create pull requests.
$user = ""
$token = "$(System.AccessToken)"
$branchTarget = "$(Build.SourceBranch)"
$branchSource = "refs/heads/master"
$branchTragetPath = $branchTarget -replace "refs/heads/", ""
$teamProject = "$(System.TeamProject)"
$repoName = "$(Build.Repository.Name)"
$orgUrl = "$(System.CollectionUri)"
$base64AuthInfo = [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes(("{0}:{1}" -f $user,$token)))
$uriBranchStatus = "$orgUrl/$teamProject/_apis/git/repositories/$repoName/stats/branches?name=$branchTragetPath&api-version=5.1"
$uriCheckActivePR = "$orgUrl/$teamProject/_apis/git/repositories/$repoName/pullrequests?searchCriteria.targetRefName=$branchTarget&searchCriteria.sourceRefName=$branchSource&api-version=5.1"
$uriCreatePR = "$orgUrl/$teamProject/_apis/git/repositories/$repoName/pullrequests?api-version=5.1"
$resultStatus = Invoke-RestMethod -Uri $uriBranchStatus -Method Get -ContentType "application/json" -Headers #{Authorization=("Basic {0}" -f $base64AuthInfo)}
if ($resultStatus.behindCount -eq 0)
{
Write-Host "Current branch contains last changes from master"
Return
}
$resultActivePR = Invoke-RestMethod -Uri $uriCheckActivePR -Method Get -ContentType "application/json" -Headers #{Authorization=("Basic {0}" -f $base64AuthInfo)}
if ($resultActivePR.count -gt 0)
{
Write-Host "PR exists already"
Return
}
$bodyCreatePR = "{sourceRefName:'$branchSource',targetRefName:'$branchTarget',title:'Sync changes from $branchSource'}"
$result = Invoke-RestMethod -Uri $uriCreatePR -Method Post -ContentType "application/json" -Headers #{Authorization=("Basic {0}" -f $base64AuthInfo)} -Body $bodyCreatePR
Write-Host "Created PR" $result.pullRequestId