Add tag-triggered release zip workflow

.github/workflows/release.yaml

@@ -0,0 +1,76 @@
+name: Release
+
+on:
+  push:
+    tags:
+      # Tags in this repo are semver without a leading v (e.g. 0.19.0).
+      - "[0-9]+.[0-9]+.*"
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: "Existing tag to publish a release asset for (e.g. 0.19.0)"
+        required: true
+        type: string
+
+permissions: {}
+
+jobs:
+  release:
+    name: Release
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: write
+
+    steps:
+      - name: Resolve version
+        id: version
+        env:
+          DISPATCH_TAG: ${{ inputs.tag }}
+        run: |
+          set -euo pipefail
+          if [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
+            VERSION="$DISPATCH_TAG"
+          else
+            VERSION="${GITHUB_REF_NAME}"
+          fi
+          if [[ ! "$VERSION" =~ ^[0-9]+\.[0-9]+ ]]; then
+            echo "::error::Unexpected tag '$VERSION'" >&2
+            exit 1
+          fi
+          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
+
+      - name: Checkout tag
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v4.2.2
+        with:
+          ref: ${{ steps.version.outputs.version }}
+          persist-credentials: false
+
+      - name: Create release archive
+        env:
+          VERSION: ${{ steps.version.outputs.version }}
+        run: |
+          set -euo pipefail
+          git archive --format=zip \
+            --prefix="bash-env-nushell-${VERSION}/" \
+            -o "bash-env-nushell-${VERSION}.zip" \
+            HEAD
+
+      - name: Create release and upload asset
+        env:
+          VERSION: ${{ steps.version.outputs.version }}
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          set -euo pipefail
+          if gh release view "$VERSION" --repo "$GITHUB_REPOSITORY" >/dev/null 2>&1; then
+            gh release upload "$VERSION" \
+              "bash-env-nushell-${VERSION}.zip" \
+              --repo "$GITHUB_REPOSITORY" \
+              --clobber
+          else
+            gh release create "$VERSION" \
+              "bash-env-nushell-${VERSION}.zip" \
+              --repo "$GITHUB_REPOSITORY" \
+              --title "$VERSION" \
+              --generate-notes
+          fi