FINERACT-2081: breaking api change test merge base instead of develop to prevent false flags

Author: budaidev

.github/workflows/verify-api-backward-compatibility.yml

@@ -23,6 +23,32 @@ jobs:
           fetch-depth: 0
           path: baseline
 
+      - name: Checkout PR branch
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v5
+        with:
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+          path: current
+
+      - name: Compute merge-base commit
+        id: merge-base
+        run: |
+          cd baseline
+          # For fork PRs, fetch PR head from the local current/ checkout
+          git fetch "${GITHUB_WORKSPACE}/current" HEAD --no-tags 2>/dev/null || true
+          MERGE_BASE=$(git merge-base ${{ github.event.pull_request.base.ref }} ${{ github.event.pull_request.head.sha }})
+          echo "Merge-base commit: ${MERGE_BASE}"
+          echo "sha=${MERGE_BASE}" >> "$GITHUB_OUTPUT"
+          BASE_HEAD=$(git rev-parse ${{ github.event.pull_request.base.ref }})
+          if [ "${MERGE_BASE}" != "${BASE_HEAD}" ]; then
+            echo "::notice::PR is not rebased on latest ${{ github.event.pull_request.base.ref }}. Using merge-base ${MERGE_BASE} as baseline (branch HEAD: ${BASE_HEAD})."
+          fi
+
+      - name: Reset baseline to merge-base
+        working-directory: baseline
+        run: git checkout ${{ steps.merge-base.outputs.sha }}
+
       - name: Set up JDK 21
         uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5
         with:
@@ -33,14 +59,6 @@ jobs:
         working-directory: baseline
         run: ./gradlew :fineract-provider:resolve --no-daemon
 
-      - name: Checkout PR branch
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v5
-        with:
-          repository: ${{ github.event.pull_request.head.repo.full_name }}
-          ref: ${{ github.event.pull_request.head.sha }}
-          fetch-depth: 0
-          path: current
-
       - name: Generate PR spec
         working-directory: current
         run: ./gradlew :fineract-provider:resolve --no-daemon