Fix failing builds during force-pushes

Author: Bart Koelman

Build.ps1

@@ -39,15 +39,15 @@ function RunCleanupCode {
     # When running in cibuild for a pull request, this reformats only the files changed in the PR and fails if the reformat produces changes.
 
     if ($env:APPVEYOR_PULL_REQUEST_HEAD_COMMIT) {
-        Write-Output "Running code cleanup in cibuild for pull request"
+        Write-Output "Running code cleanup on changed files in pull request"
 
-        $sourceCommitHash = $env:APPVEYOR_PULL_REQUEST_HEAD_COMMIT
+        # In the past, we used $env:APPVEYOR_PULL_REQUEST_HEAD_COMMIT for the merge commit hash. That is the pinned hash at the time the build is enqueued.
+        # When a force-push happens after that, while the build hasn't yet started, this hash becomes invalid during the build, resulting in a lookup error.
+        # To prevent failing the build for unobvious reasons we use HEAD, which is always the latest version.
+        $mergeCommitHash = git rev-parse "HEAD"
         $targetCommitHash = git rev-parse "$env:APPVEYOR_REPO_BRANCH"
 
-        Write-Output "Source commit hash = $sourceCommitHash"
-        Write-Output "Target commit hash = $targetCommitHash"
-
-        dotnet regitlint -s JsonApiDotNetCore.sln --print-command --jb --profile --jb --profile='\"JADNC Full Cleanup\"' --jb --properties:Configuration=Release --jb --verbosity=WARN -f commits -a $sourceCommitHash -b $targetCommitHash --fail-on-diff --print-diff
+        dotnet regitlint -s JsonApiDotNetCore.sln --print-command --jb --profile --jb --profile='\"JADNC Full Cleanup\"' --jb --properties:Configuration=Release --jb --verbosity=WARN -f commits -a $mergeCommitHash -b $targetCommitHash --fail-on-diff --print-diff
         CheckLastExitCode
     }
 }