Fix PR creation on GitHub App auth path (pass --head to gh pr create)

The GitHub App auth generation path clones repos with `git clone --depth 1`,
which implies --single-branch and only tracks the base branch. After pushing
the generated feature branch, no `refs/remotes/origin/<branch>` tracking ref
exists locally, so `gh pr create` (which auto-detects the pushed head via that
ref) aborts with "you must first push the current branch to a remote, or use
the --head flag" even though the push succeeded.

- create-pull-request.ps1: pass `-H $env:BranchName` and `-R $env:RepoName` to
  `gh pr create`, and fail the step on a non-zero exit code instead of always
  printing "Pull Request Created successfully."
- language-generation-kiota.yml: thread `BranchName` into the
  create-pull-request.ps1 step env so the head branch is available.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jingjingjia-ms

.azure-pipelines/generation-templates/language-generation-kiota.yml

@@ -166,6 +166,7 @@ steps:
   displayName: 'Create Pull Request for the generated build for ${{ parameters.repoName }}'
   env:
     BaseBranch: ${{ parameters.baseBranchName}}
+    BranchName: ${{ parameters.branchName }}
     GeneratePullRequest: ${{ parameters.generatePullRequest}}
     GhAppId: $(microsoft-graph-devx-bot-appid)
     GhAppKey: $(microsoft-graph-devx-bot-privatekey)

scripts/create-pull-request.ps1

@@ -30,13 +30,30 @@ if (![string]::IsNullOrEmpty($env:BaseBranch))
     $baseBranchParameter = "-B $env:BaseBranch" # optionally pass the base branch if provided as the PR will target the default branch otherwise
 }
 
+$headBranchParameter = ""
+
+if (![string]::IsNullOrEmpty($env:BranchName))
+{
+    # Explicitly set the head branch. On the GitHub App auth path the repository is cloned with
+    # 'git clone --depth 1', which implies --single-branch and only tracks the base branch. As a
+    # result no 'refs/remotes/origin/<branch>' tracking ref exists after pushing, so 'gh pr create'
+    # cannot auto-detect that the branch was pushed and aborts with "you must first push the current
+    # branch to a remote, or use the --head flag". Passing --head bypasses that detection.
+    $headBranchParameter = "-H $env:BranchName"
+}
+
 # The installed application is required to have the following permissions: read/write on pull requests/
 $tokenGenerationScript = "$env:ScriptsDirectory\Generate-Github-Token.ps1"
 $env:GITHUB_TOKEN = & $tokenGenerationScript -AppClientId $env:GhAppId -AppPrivateKeyContents $env:GhAppKey -Repository $env:RepoName
 Write-Host "Fetched Github Token for PR generation and set as environment variable."
 
 # No need to specify reviewers as code owners should be added automatically.
 Invoke-Expression "gh auth login" # login to GitHub
-Invoke-Expression "gh pr create -t ""$title"" -b ""$body"" $baseBranchParameter | Write-Host"
+Invoke-Expression "gh pr create -R ""$env:RepoName"" -t ""$title"" -b ""$body"" $baseBranchParameter $headBranchParameter | Write-Host"
+
+if ($LASTEXITCODE -ne 0)
+{
+    throw "Failed to create pull request for $env:RepoName (branch '$env:BranchName'). 'gh pr create' exited with code $LASTEXITCODE."
+}
 
 Write-Host "Pull Request Created successfully."