[bazel/infra] Automate publish to BCR workflow (#1686)

Signed-off-by: Shameek Ganguly <shameek@intrinsic.ai>

Author: shameekganguly

.github/workflows/publish.yaml

@@ -1,13 +1,19 @@
 # Publish new releases to Bazel Central Registry.
 name: Publish to BCR
 on:
-  # For now, the workflow must be manually triggered.
+  # Manual trigger
   workflow_dispatch:
     inputs:
       tag_name:
         description: git tag being released
         required: true
         type: string
+
+  # Automated trigger on git tag push
+  push:
+    tags:
+      # Glob pattern: branch_semver-postfix
+      - 'sdformat[1-9]?[0-9]_[0-9]+.[0-9]+.[0-9]+*'
 jobs:
   # The publish-to-bcr reusable workflow expects the version name to be in
   # semver-(optional build metadata postfix) format, but the repo tags are in
@@ -17,23 +23,31 @@ jobs:
     runs-on: ubuntu-latest
     outputs:
       prefix: ${{ steps.extract.outputs.prefix }}
+      tag_name: ${{ steps.extract.outputs.tag_name }}
     steps:
-      - name: Extract the tag prefix from the tag name.
+      - name: Determine tag name and prefix
         id: extract
         run: |
-          branch=$(echo "${{ inputs.tag_name }}" | cut -d'_' -f1)
+          # Use input if manual, otherwise use the ref_name from the push event
+          TAG_NAME="${{ inputs.tag_name || github.ref_name }}"
+
+          # Extract prefix (everything before the underscore)
+          branch=$(echo "$TAG_NAME" | cut -d'_' -f1)
           prefix="${branch}_"
-          echo "prefix=${prefix}" | tee -a "$GITHUB_OUTPUT"
+
+          echo "tag_name=$TAG_NAME" >> "$GITHUB_OUTPUT"
+          echo "prefix=$prefix" >> "$GITHUB_OUTPUT"
 
   publish:
     needs: extract_tag_prefix
     uses: bazel-contrib/publish-to-bcr/.github/workflows/publish.yaml@v1.0.0
     with:
-      tag_name: ${{ inputs.tag_name }}
+      tag_name: ${{ needs.extract_tag_prefix.outputs.tag_name }}
       # GitHub repository which is a fork of the upstream where the Pull Request will be opened.
       registry_fork: gazebo-forks/bazel-central-registry
       attest: false
       tag_prefix: ${{ needs.extract_tag_prefix.outputs.prefix }}
+      draft: false
 
     permissions:
       attestations: write