chore: create workflow to check showcase commit (#13305)

A workflow to make sure the showcase commit is the same as what is in
librarian. If the workflow fails, or there is a mismatch, an issue will
be created.

Fixes googleapis/librarian#6200

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: sofisl

.github/workflows/showcase-version-check.yaml

@@ -0,0 +1,96 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: Showcase Version Check
+
+on:
+  schedule:
+    - cron: '30 3 * * *' # Run daily at 3:30 AM UTC
+  workflow_dispatch: # Allow manual trigger
+  pull_request:
+    paths:
+      - 'librarian.yaml'
+      - 'java-showcase/gapic-showcase/pom.xml'
+      - '.github/workflows/showcase-version-check.yaml'
+
+jobs:
+  check-version:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+    steps:
+      - uses: actions/checkout@v4
+      - name: Extract showcase version from pom.xml
+        id: extract_version
+        shell: bash
+        run: |
+          version=$(awk -F'[<>]' '/gapic-showcase.version/{print $3; exit}' java-showcase/gapic-showcase/pom.xml)
+          echo "version=$version" >> "$GITHUB_OUTPUT"
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.24'
+      - name: Extract showcase commit from librarian.yaml
+        id: extract_commit
+        shell: bash
+        run: |
+          version=$(go run github.com/googleapis/librarian/cmd/librarian@latest config get version)
+          commit=$(go run "github.com/googleapis/librarian/cmd/librarian@${version}" config get sources.showcase.commit)
+          echo "commit=$commit" >> "$GITHUB_OUTPUT"
+      - name: Verify showcase version and commit match
+        shell: bash
+        run: |
+          # 1. Query the remote repository for the specific version tag
+          REMOTE_URL="https://github.com/googleapis/gapic-showcase.git"
+          TAG_NAME="v${{ steps.extract_version.outputs.version }}"
+          
+          OUTPUT=$(git ls-remote "$REMOTE_URL" "refs/tags/$TAG_NAME")
+          
+          if [ -z "$OUTPUT" ]; then
+            echo "Error: Tag $TAG_NAME not found on remote $REMOTE_URL"
+            exit 1
+          fi
+          
+          # 2. Grab the commit hash from the very last line of the output
+          EXPECTED_COMMIT=$(echo "$OUTPUT" | tail -n 1 | awk '{print $1}')
+          
+          echo "Expected commit for tag $TAG_NAME: $EXPECTED_COMMIT"
+          echo "Current librarian commit: ${{ steps.extract_commit.outputs.commit }}"
+          
+          # 3. Cross-reference with librarian.yaml
+          if [ "${{ steps.extract_commit.outputs.commit }}" != "$EXPECTED_COMMIT" ]; then
+            echo "Mismatch: librarian.yaml has commit '${{ steps.extract_commit.outputs.commit }}', but tag '$TAG_NAME' is at commit '$EXPECTED_COMMIT'"
+            echo "MISMATCH=true" >> "$GITHUB_ENV"
+            exit 2
+          fi
+          
+          echo "Showcase version and commit are in sync!"
+      - name: Create issue on mismatch
+        if: failure() && env.MISMATCH == 'true'
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          gh issue create \
+            -R "${{ github.repository }}" \
+            -t "Showcase Version Mismatch: librarian.yaml and pom.xml out of sync" \
+            -b "The Showcase version in java-showcase/gapic-showcase/pom.xml and the commit in librarian.yaml do not match. Please update them to match. See logs: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}"
+      - name: Create issue on workflow failure
+        if: failure() && env.MISMATCH != 'true'
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          gh issue create \
+            -R "${{ github.repository }}" \
+            -t "Showcase Version Check Workflow Failure" \
+            -b "The Showcase Version Check workflow has failed due to an unexpected execution error. Please check the logs at ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }} for details."