reconfigure branch for local builds and as scheduler for docs workflows

- set up placeholder and trigger for Deploy Docs workflow in docs-build branch
- set up placeholder and trigger for Rebuild Search Index workflow in docs-build branch
- remove obsolete Deploy Reference workflow
- upgrade Antora to 3.1
- reconfigure docs build for local build only
- add patch to support using linked worktree as Antora content source
- remove Antora extensions only needed for the production docs build

docs/antora-linked-worktree-patch.js

@@ -0,0 +1,53 @@
+'use strict'
+
+/* Copyright (c) 2002-2022 the original author or authors.
+ *
+ * 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.
+ */
+const { promises: fsp } = require('fs')
+const ospath = require('path')
+
+/**
+ * Rewrites local content sources to support the use of linked worktrees.
+ *
+ * @author Dan Allen <dan@opendevise.com>
+ */
+module.exports.register = function () {
+  this.once('playbookBuilt', async ({ playbook }) => {
+    const expandPath = this.require('@antora/expand-path-helper')
+    for (const contentSource of playbook.content.sources) {
+      const { url, branches } = contentSource
+      if (url.charAt() !== '.') continue
+      const absdir = expandPath(url, { dot: playbook.dir })
+      const gitfile = ospath.join(absdir, '.git')
+      if (await fsp.stat(gitfile).then((stat) => !stat.isDirectory(), () => false)) {
+        const worktreeGitdir = await fsp.readFile(gitfile, 'utf8')
+          .then((contents) => contents.trimRight().substr(8))
+        const worktreeBranch = await fsp.readFile(ospath.join(worktreeGitdir, 'HEAD'), 'utf8')
+          .then((contents) => contents.trimRight().replace(/^ref: (?:refs\/heads\/)?/, ''))
+        const reldir = ospath.relative(
+          playbook.dir,
+          await fsp.readFile(ospath.join(worktreeGitdir, 'commondir'), 'utf8')
+            .then((contents) => {
+              const gitdir = ospath.join(worktreeGitdir, contents.trimRight())
+              return ospath.basename(gitdir) === '.git' ? ospath.dirname(gitdir) : gitdir
+            })
+        )
+        contentSource.url = reldir ? `.${ospath.sep}${reldir}` : '.'
+        if (!branches) continue
+        contentSource.branches = (branches.constructor === Array ? branches : [branches])
+          .map((pattern) => pattern.replaceAll('HEAD', worktreeBranch))
+      }
+    }
+  })
+}