Add a version switcher for RTD (#144)

* Add a version switcher for RTD

---------

Co-authored-by: Jean-Philippe Lenain <[email protected]>

README.md

@@ -1,4 +1,4 @@
-# nectarchain [![Build Status](https://github.com/cta-observatory/nectarchain/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/cta-observatory/nectarchain/actions/workflows/ci.yml?query=workflow%3ACI+branch%3Amain) [![pypi](https://badge.fury.io/py/nectarchain.svg)](https://pypi.org/project/nectarchain) [![conda](https://anaconda.org/conda-forge/nectarchain/badges/version.svg)](https://anaconda.org/conda-forge/nectarchain) [![codecov](https://codecov.io/github/cta-observatory/nectarchain/graph/badge.svg?token=TDhZlJtbMv)](https://codecov.io/github/cta-observatory/nectarchain)
+# nectarchain [![Build Status](https://github.com/cta-observatory/nectarchain/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/cta-observatory/nectarchain/actions/workflows/ci.yml?query=workflow%3ACI+branch%3Amain) [![pypi](https://badge.fury.io/py/nectarchain.svg)](https://pypi.org/project/nectarchain) [![conda](https://anaconda.org/conda-forge/nectarchain/badges/version.svg)](https://anaconda.org/conda-forge/nectarchain) [![codecov](https://codecov.io/github/cta-observatory/nectarchain/graph/badge.svg?token=TDhZlJtbMv)](https://codecov.io/github/cta-observatory/nectarchain/tree/main) [![Documentation Status](https://readthedocs.org/projects/nectarchain/badge/?version=latest)](https://nectarchain.readthedocs.io/en/latest/?badge=latest)
 
 Repository for the high level analysis of the NectarCAM data.
 The analysis is heavily based on [ctapipe](https://github.com/cta-observatory/ctapipe), adding custom code for NectarCAM calibration.

docs/_static/switcher.json

@@ -0,0 +1,12 @@
+[
+  {
+    "name": "dev",
+    "version": "latest",
+    "url": "https://nectarchain.readthedocs.io/en/latest/"
+  },
+  {
+    "name": "stable",
+    "version": "stable",
+    "url": "https://nectarchain.readthedocs.io/en/stable/"
+  }
+]

docs/conf.py

@@ -6,6 +6,7 @@
 # -- Project information -----------------------------------------------------
 # https://www.sphinx-doc.org/en/master/usage/configuration.html#project-information
 import datetime
+import os
 import sys
 from pathlib import Path
 
@@ -116,6 +117,27 @@
 # If true, `todo` and `todoList` produce output, else they produce nothing.
 todo_include_todos = True
 
+
+# -- Version switcher -----------------------------------------------------
+
+# Define the json_url for our version switcher.
+json_url = "https://nectarchain.readthedocs.io/en/latest/_static/switcher.json"
+
+# Define the version we use for matching in the version switcher.,
+version_match = os.getenv("READTHEDOCS_VERSION")
+# If READTHEDOCS_VERSION doesn't exist, we're not on RTD
+# If it is an integer, we're in a PR build and the version isn't correct.
+if not version_match or version_match.isdigit():
+    # For local development, infer the version to match from the package.
+    if "dev" in release or "rc" in release:
+        version_match = "latest"
+    else:
+        version_match = release
+
+    # We want to keep the relative reference when on a pull request or locally
+    json_url = "_static/switcher.json"
+
+
 # -- Options for HTML output -------------------------------------------------
 # https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-html-output
 
@@ -146,7 +168,12 @@
     },
     "navigation_with_keys": False,
     "github_url": f"https://github.com/cta-observatory/{project}",
+    "header_links_before_dropdown": 6,
     "navbar_start": ["navbar-logo", "version-switcher"],
+    "switcher": {
+        "version_match": version_match,
+        "json_url": json_url,
+    },
     "announcement": """
         <p>nectarchain is not stable yet, so expect large and rapid
         changes to structure and functionality as we explore various