Fix Labeller?

Author: Happypig375

.github/workflows/Label.yml

@@ -8,12 +8,13 @@ jobs:
       pull-requests: write # allow adding a label to this pull request
     steps:
     - uses: actions/checkout@v6
+      with:
+        fetch-depth: 0 # fetch all commit history and tags, instead of the default fetch of only one commit
+        ref: ${{ github.event.pull_request.head.sha }}  # checkout the PR branch
     - name: If there are changes in PublicApi.Shipped.txt, fail the workflow
       if: github.head_ref != 'action/ship-publicapi' # Same branch name specified in Release.yml
       run: |
-        $head = git rev-parse HEAD
-        Write-Output "HEAD is $head"
-        $changes = git diff --numstat --shortstat HEAD..${{ github.sha }} -- '**/PublicApi.Shipped.txt'
+        $changes = git diff --numstat --shortstat origin/${{ github.base_ref }}...HEAD -- '**/PublicApi.Shipped.txt'
         Write-Output "$changes"
         if ($changes) {
           Write-Error "Changes detected in PublicApi.Shipped.txt files. Public API changes must be shipped through the release process, not in regular pull requests."
@@ -22,13 +23,12 @@ jobs:
       shell: pwsh
     - name: Label based on PublicApi.Unshipped.txt
       run: |
-        # Determine the appropriate label (Sync these labels with release-drafter.yml)
-        if ("${{ github.ref }}" -eq "action/ship-publicapi") { # Same branch name specified in Release.yml
+        if ("${{ github.head_ref }}" -eq "action/ship-publicapi") {
           $labels = @('Type/Housekeeping')
           Write-Output "This is a ship-publicapi PR, labeling as Type/Maintenance"
         } else {
           # For regular PRs, check for API changes
-          $changes = git diff HEAD..${{ github.sha }} -- '**/PublicApi.Unshipped.txt'
+          $changes = git diff origin/${{ github.base_ref }}...HEAD -- '**/PublicApi.Unshipped.txt'
           Write-Output "$changes"
           
           if ($changes) {