ci: add manual release workflow for non-version-bump improvements

.github/workflows/auto-release.yml

@@ -7,7 +7,8 @@ on:
       - docker-bake.hcl
 
 concurrency:
-  group: auto-release-${{ github.workflow }}-${{ github.ref }}
+  # Shared with release.yml so a manual dispatch can't allocate the same tag.
+  group: release-tag-creation
   cancel-in-progress: false
 
 permissions: {}
@@ -60,32 +61,9 @@ jobs:
   tag-and-release:
     needs: check-version-bump
     if: needs.check-version-bump.outputs.bumped == 'true'
-    runs-on: ubuntu-latest
     permissions:
       contents: write
-    steps:
-      - name: Checkout
-        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # actions/checkout@v5
-        with:
-          persist-credentials: false
-
-      - name: Create release tag and GitHub release
-        env:
-          GH_TOKEN: ${{ github.token }}
-        run: |
-          set -euo pipefail
-          base="release/$(date -u +%Y%m%d)"
-          tag="${base}"
-          suffix=1
-          while gh api "repos/${{ github.repository }}/git/ref/tags/${tag}" >/dev/null 2>&1; do
-            tag="${base}-${suffix}"
-            suffix=$((suffix + 1))
-          done
-
-          gh release create "${tag}" \
-            --target "${{ github.sha }}" \
-            --title "${tag}" \
-            --generate-notes
+    uses: ./.github/workflows/cut-release.yml
 
   publish:
     needs: tag-and-release

.github/workflows/cut-release.yml

@@ -0,0 +1,69 @@
+# Shared by auto-release.yml (version-bump trigger) and release.yml (manual
+# dispatch): create a date-based (release/YYYYMMDD) GitHub release tag, with a
+# numeric suffix on a same-day re-release, or an explicit override tag.
+name: cut-release
+
+on:
+  workflow_call:
+    inputs:
+      tag:
+        description: "Override tag; empty uses release/YYYYMMDD with a numeric suffix on collision."
+        required: false
+        type: string
+        default: ""
+
+permissions: {}
+
+jobs:
+  cut:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # actions/checkout@v5
+        with:
+          persist-credentials: false
+
+      - name: Create release tag and GitHub release
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+          OVERRIDE: ${{ inputs.tag }}
+          SHA: ${{ github.sha }}
+        run: |
+          set -euo pipefail
+
+          # 0 = the tag exists; 1 = confirmed absent (HTTP 404). Any other
+          # failure (network, rate limit, auth) aborts the job -- a lookup we
+          # can't complete must never be mistaken for "tag is free".
+          tag_taken() {
+            local out
+            if out="$(gh api "repos/${GH_REPO}/git/ref/tags/$1" 2>&1)"; then
+              return 0
+            fi
+            if printf '%s\n' "$out" | grep -qiE 'HTTP 404|Not Found'; then
+              return 1
+            fi
+            echo "::error::tag lookup for '$1' failed: ${out}"
+            exit 1
+          }
+
+          if [ -n "${OVERRIDE}" ]; then
+            tag="${OVERRIDE}"
+            if tag_taken "${tag}"; then
+              echo "::error::tag ${tag} already exists"; exit 1
+            fi
+          else
+            base="release/$(date -u +%Y%m%d)"
+            tag="${base}"; n=1
+            while tag_taken "${tag}"; do
+              tag="${base}-${n}"; n=$((n + 1))
+            done
+          fi
+
+          echo "Cutting release ${tag} at ${SHA}"
+          gh release create "${tag}" \
+            --target "${SHA}" \
+            --title "${tag}" \
+            --generate-notes

.github/workflows/release.yml

@@ -0,0 +1,37 @@
+# Manual release, for improvements that don't bump a tracked upstream
+# version and so wouldn't trigger auto-release.yml.
+name: release
+
+on:
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: "Override tag (default: release/YYYYMMDD). Must not already exist."
+        required: false
+        type: string
+
+permissions: {}
+
+concurrency:
+  # Shared with auto-release.yml so it can't allocate the same tag.
+  group: release-tag-creation
+  cancel-in-progress: false
+
+jobs:
+  tag-and-release:
+    permissions:
+      contents: write
+    uses: ./.github/workflows/cut-release.yml
+    with:
+      tag: ${{ inputs.tag }}
+
+  publish:
+    needs: tag-and-release
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+    uses: ./.github/workflows/publish.yml
+    secrets:
+      dockerhub_user: ${{ secrets.dockerhub_user }}
+      dockerhub_token: ${{ secrets.dockerhub_token }}