Fix detect-netsdk-diagnostics action false positives

.github/workflows/detect-netsdk-diagnostics.yml

@@ -26,13 +26,14 @@ on:
 permissions: read-all
 
 jobs:
-  read-diff:
-    name: Read .xlf Diff
+  detect-diagnostics:
+    name: Detect New NETSDK Diagnostic Codes
     runs-on: ubuntu-latest
     permissions:
       contents: read
     outputs:
-      xlf_diff: ${{ steps.get-diff.outputs.xlf_diff }}
+      found_diagnostics: ${{ steps.detect.outputs.found_diagnostics }}
+      has_diagnostics: ${{ steps.detect.outputs.has_diagnostics }}
 
     steps:
       - name: Checkout base branch
@@ -55,39 +56,24 @@ jobs:
           GITHUB_TOKEN: ""
           GH_TOKEN: ""
         run: |
-          # Get diff only from .xlf files between base and PR head
-          DIFF_OUTPUT=$(git diff ${{ github.event.pull_request.base.sha }}..${{ github.event.pull_request.head.sha }} -- '*.xlf')
+          # Get diff of .xlf files changed by this PR.
+          # Use three-dot diff (merge-base) so that only the PR's changes are included,
+          # not unrelated changes on the target branch that the PR hasn't been rebased onto.
+          DIFF_OUTPUT=$(git diff ${{ github.event.pull_request.base.sha }}...${{ github.event.pull_request.head.sha }} -- '*.xlf')
 
-          # Check diff size to prevent resource exhaustion (limit to ~1MB)
-          DIFF_SIZE=$(echo "$DIFF_OUTPUT" | wc -c)
-          if [ "$DIFF_SIZE" -gt 1048576 ]; then
-            echo "Error: Diff size ($DIFF_SIZE bytes) exceeds 1MB limit"
-            exit 1
-          fi
-
-          # Use multiline output for job outputs
+          # Use multiline output for step outputs
           # https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#multiline-strings
           {
             echo 'xlf_diff<<EOF'
             echo "$DIFF_OUTPUT"
             echo 'EOF'
           } >> "$GITHUB_OUTPUT"
 
-  detect-diagnostics:
-    name: Detect New NETSDK Diagnostic Codes
-    runs-on: ubuntu-latest
-    needs: read-diff
-    permissions: {}
-    outputs:
-      found_diagnostics: ${{ steps.detect.outputs.found_diagnostics }}
-      has_diagnostics: ${{ steps.detect.outputs.has_diagnostics }}
-
-    steps:
       - name: Detect new NETSDK diagnostics
         id: detect
         uses: actions/github-script@f28e40c7f34bde8b3046d885e986cb6290c5673b # v7
         env:
-          XLF_DIFF: ${{ needs.read-diff.outputs.xlf_diff }}
+          XLF_DIFF: ${{ steps.get-diff.outputs.xlf_diff }}
         with:
           script: |
             const diff = process.env.XLF_DIFF;