docs: deploy docs to production server from CI

docs/sanitize_version.py

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+# Tiny Python module to sanitize a Git version into something that can be used in a URL
+#
+# (this is used in multiple places: conf_common.py and in tools/ci/docs_deploy
+#
+# Copyright 2020 Espressif Systems (Shanghai) PTE LTD
+#
+# 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
+#
+#     http://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.
+import os
+
+
+def sanitize_version(original_version):
+    """ Given a version (probably output from 'git describe --always' or similar), return
+    a URL-safe sanitized version. (this is used as 'release' config variable when building
+    the docs.)
+
+    Will override the original version with the Gitlab CI CI_COMMIT_REF_NAME environment variable if
+    this is present.
+
+    Also follows the RTD-ism that master branch is named 'latest'
+
+    """
+
+    try:
+        version = os.environ['CI_COMMIT_REF_NAME']
+    except KeyError:
+        version = original_version
+
+    if version == "master":
+        return "latest"
+
+    version = version.replace('/', '-')
+
+    return version