Add documentation publishing workflow (#730)

Adds a documentation publishing workflow as a part of
https://github.com/astral-sh/ty/pull/729 but is based on `main` so we
can test the workflow dispatch against the branch.

This is copied from ruff with updated names.

.github/workflows/publish-docs.yml

@@ -0,0 +1,147 @@
+# Publish the ty documentation.
+#
+# Assumed to run as a subworkflow of .github/workflows/release.yml; specifically, as a post-announce
+# job within `cargo-dist`.
+name: mkdocs
+
+on:
+  workflow_dispatch:
+    inputs:
+      ref:
+        description: "The commit SHA, tag, or branch to publish. Uses the default branch if not specified."
+        default: ""
+        type: string
+  workflow_call:
+    inputs:
+      plan:
+        required: true
+        type: string
+
+permissions:
+  contents: read
+
+jobs:
+  mkdocs:
+    runs-on: ubuntu-latest
+    env:
+      MKDOCS_INSIDERS_SSH_KEY_EXISTS: ${{ secrets.MKDOCS_INSIDERS_SSH_KEY != '' }}
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          ref: ${{ inputs.ref }}
+          persist-credentials: true
+
+      - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        with:
+          python-version: 3.12
+
+      - name: "Set docs version"
+        env:
+          version: ${{ (inputs.plan != '' && fromJson(inputs.plan).announcement_tag) || inputs.ref }}
+        run: |
+          # if version is missing, use 'latest'
+          if [ -z "$version" ]; then
+            echo "Using 'latest' as version"
+            version="latest"
+          fi
+
+          # Use version as display name for now
+          display_name="$version"
+
+          echo "version=$version" >> "$GITHUB_ENV"
+          echo "display_name=$display_name" >> "$GITHUB_ENV"
+
+      - name: "Set branch name"
+        run: |
+          timestamp="$(date +%s)"
+
+          # create branch_display_name from display_name by replacing all
+          # characters disallowed in git branch names with hyphens
+          branch_display_name="$(echo "${display_name}" | tr -c '[:alnum:]._' '-' | tr -s '-')"
+
+          echo "branch_name=update-docs-$branch_display_name-$timestamp" >> "$GITHUB_ENV"
+          echo "timestamp=$timestamp" >> "$GITHUB_ENV"
+
+      - name: "Add SSH key"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
+        uses: webfactory/ssh-agent@a6f90b1f127823b31d4d4a8d96047790581349bd # v0.9.1
+        with:
+          ssh-private-key: ${{ secrets.MKDOCS_INSIDERS_SSH_KEY }}
+
+      - name: "Install Rust toolchain"
+        run: rustup show
+
+      - uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
+
+      - name: "Install Insiders dependencies"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
+        run: pip install -r docs/requirements-insiders.txt
+
+      - name: "Install dependencies"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS != 'true' }}
+        run: pip install -r docs/requirements.txt
+
+      - name: "Copy README File"
+        run: |
+          python scripts/transform_readme.py --target mkdocs
+          python scripts/generate_mkdocs.py
+
+      - name: "Build Insiders docs"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
+        run: mkdocs build --strict -f mkdocs.insiders.yml
+
+      - name: "Build docs"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS != 'true' }}
+        run: mkdocs build --strict -f mkdocs.public.yml
+
+      - name: "Clone docs repo"
+        run: git clone https://${{ secrets.ASTRAL_DOCS_PAT }}@github.com/astral-sh/docs.git astral-docs
+
+      - name: "Copy docs"
+        run: rm -rf astral-docs/site/ty && mkdir -p astral-docs/site && cp -r site/ty astral-docs/site/
+
+      - name: "Commit docs"
+        working-directory: astral-docs
+        run: |
+          git config user.name "astral-docs-bot"
+          git config user.email "176161322+astral-docs-bot@users.noreply.github.com"
+
+          git checkout -b "${branch_name}"
+          git add site/ty
+          git commit -m "Update ty documentation for $version"
+
+      - name: "Create Pull Request"
+        working-directory: astral-docs
+        env:
+          GITHUB_TOKEN: ${{ secrets.ASTRAL_DOCS_PAT }}
+        run: |
+          # set the PR title
+          pull_request_title="Update ty documentation for ${display_name}"
+
+          # Delete any existing pull requests that are open for this version
+          # by checking against pull_request_title because the new PR will
+          # supersede the old one.
+          gh pr list --state open --json title --jq '.[] | select(.title == "$pull_request_title") | .number' | \
+            xargs -I {} gh pr close {}
+
+          # push the branch to GitHub
+          git push origin "${branch_name}"
+
+          # create the PR
+          gh pr create \
+            --base=main \
+            --head="${branch_name}" \
+            --title="${pull_request_title}" \
+            --body="Automated documentation update for ${display_name}" \
+            --label="documentation"
+
+      - name: "Merge Pull Request"
+        if: ${{ inputs.plan != '' && !fromJson(inputs.plan).announcement_tag_is_implicit }}
+        working-directory: astral-docs
+        env:
+          GITHUB_TOKEN: ${{ secrets.ASTRAL_DOCS_PAT }}
+        run: |
+          # auto-merge the PR if the build was triggered by a release. Manual builds should be reviewed by a human.
+          # give the PR a few seconds to be created before trying to auto-merge it
+          sleep 10
+          gh pr merge --squash "${branch_name}"