Add LAMMPS_WEBSITE_BASEURL env variable to set canonical URL in docs

doc/utils/sphinx-config/_themes/lammps_theme/layout.html

@@ -38,10 +38,11 @@
   {% if favicon %}
     <link rel="shortcut icon" href="{{ pathto('_static/' + favicon, 1) }}"/>
   {% endif %}
-  {# CANONICAL URL #}
-  {% if theme_canonical_url %}
-    <link rel="canonical" href="{{ theme_canonical_url }}{{ pagename }}.html"/>
-  {% endif %}
+
+  {#- CANONICAL URL #}
+  {%- if pageurl %}
+    <link rel="canonical" href="{{ pageurl|e }}" />
+  {%- endif -%}
 
   {# JAVASCRIPTS #}
   {%- block scripts %}

doc/utils/sphinx-config/_themes/lammps_theme/theme.conf

@@ -4,7 +4,6 @@ stylesheet = css/theme.css
 pygments_style = default
 
 [options]
-canonical_url =
 analytics_id =
 collapse_navigation = False
 sticky_navigation = False

doc/utils/sphinx-config/conf.py.in

@@ -255,6 +255,8 @@ htmlhelp_basename = 'LAMMPSdoc'
 
 html_permalinks = True
 
+html_baseurl = os.environ.get('LAMMPS_WEBSITE_BASEURL', '')
+
 if 'epub' in sys.argv:
   html_math_renderer = 'imgmath'
 else: