workflows/L4LB: Apply fixes to change detection logic

Commit 98e6ea4 ("workflows: Improve the change check for issue_comment
triggers") and its subsequent fix (see previous commit) missed the L4LB
workflow. This commit fixes it by applying the same modifications to the
L4LB workflow.

Fix: 98e6ea4 ("workflows: Improve the change check for issue_comment triggers")
Signed-off-by: Paul Chaignon <paul@cilium.io>

.github/workflows/tests-l4lb-v1.10.yaml

@@ -77,20 +77,30 @@ jobs:
     outputs:
       tested: ${{ steps.tested-tree.outputs.src }}
     steps:
-      - name: Retrieve pull request's base and head
-        if: ${{ github.event.issue.pull_request }}
-        id: pr
-        run: |
-          curl ${{ github.event.issue.pull_request.url }} > pr.json
-          echo "::set-output name=base::$(jq -r '.base.sha' pr.json)"
-          echo "::set-output name=head::$(jq -r '.head.sha' pr.json)"
       # Because we run on issue comments, we need to checkout the code for
       # paths-filter to work.
       - name: Checkout code
         if: ${{ github.event.issue.pull_request }}
         uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
         with:
           persist-credentials: false
+      - name: Retrieve pull request's base and head
+        if: ${{ github.event.issue.pull_request }}
+        id: pr
+        run: |
+          curl \
+             -H "Accept: application/vnd.github.v3+json" \
+             -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" \
+             ${{ github.event.issue.pull_request.url }} > pr.json
+          commits_url=$(jq -r '.commits_url' pr.json)
+          curl \
+             -H "Accept: application/vnd.github.v3+json" \
+             -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" \
+             ${commits_url} > commits.json
+          pr_first_sha=$(jq -r ".[0].sha" commits.json)
+          pr_parent_sha=$(git rev-parse "${pr_first_sha}^")
+          echo "::set-output name=base::${pr_parent_sha}"
+          echo "::set-output name=head::$(jq -r '.head.sha' pr.json)"
       - name: Check code changes
         if: ${{ github.event.issue.pull_request }}
         uses: dorny/paths-filter@b2feaf19c27470162a626bd6fa8438ae5b263721

.github/workflows/tests-l4lb.yaml

@@ -80,20 +80,30 @@ jobs:
     outputs:
       tested: ${{ steps.tested-tree.outputs.src }}
     steps:
-      - name: Retrieve pull request's base and head
-        if: ${{ github.event.issue.pull_request }}
-        id: pr
-        run: |
-          curl ${{ github.event.issue.pull_request.url }} > pr.json
-          echo "::set-output name=base::$(jq -r '.base.sha' pr.json)"
-          echo "::set-output name=head::$(jq -r '.head.sha' pr.json)"
       # Because we run on issue comments, we need to checkout the code for
       # paths-filter to work.
       - name: Checkout code
         if: ${{ github.event.issue.pull_request }}
         uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
         with:
           persist-credentials: false
+      - name: Retrieve pull request's base and head
+        if: ${{ github.event.issue.pull_request }}
+        id: pr
+        run: |
+          curl \
+             -H "Accept: application/vnd.github.v3+json" \
+             -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" \
+             ${{ github.event.issue.pull_request.url }} > pr.json
+          commits_url=$(jq -r '.commits_url' pr.json)
+          curl \
+             -H "Accept: application/vnd.github.v3+json" \
+             -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" \
+             ${commits_url} > commits.json
+          pr_first_sha=$(jq -r ".[0].sha" commits.json)
+          pr_parent_sha=$(git rev-parse "${pr_first_sha}^")
+          echo "::set-output name=base::${pr_parent_sha}"
+          echo "::set-output name=head::$(jq -r '.head.sha' pr.json)"
       - name: Check code changes
         if: ${{ github.event.issue.pull_request }}
         uses: dorny/paths-filter@b2feaf19c27470162a626bd6fa8438ae5b263721