Add an explicit message about thematic series in each part

themes/chosto/layouts/_default/single.html

@@ -1,7 +1,7 @@
 {{ define "main" }}
 <div class="section">
   <!--
-  If the current page is a blog post and belongs to a case, we will add a side menu
+  If the current page is a blog post and belongs to a thematic serie, we will add a side menu
   with all other blog posts belonging to that case, emphasis to the current.
   Still use empty container if nothing to show for homogeneous layout
   -->
@@ -27,13 +27,25 @@
     <section class="column content is-half">
       <div>
         <article>
+          <!-- If this is part of a thematic serie, remind it so it is clear -->
+          {{ if (and .IsPage (eq .FirstSection.Section "posts"))}}
+          {{ with .CurrentSection }}
+          {{ if .Params.Title }}
+          <div class="message is-info">
+            <div class="message-body content">
+              Le post que vous lisez fait partie du dossier « <a href="{{ .Permalink }}">{{ .Params.Title }}</a> ». Le menu sur la gauche permet de naviguer entre ses billets. Bonne lecture ! 😄
+            </div>
+          </div>
+          {{ end }}
+          {{ end }}
+          {{ end }}
           <!-- First thing is a legend for the hero image, if it exists -->
           {{ with .Params.imgExplanation }}
-          <article class="message mb-5">
+          <div class="message">
             <div class="message-body content is-italic">
               {{ . }}
             </div>
-          </article>
+          </div>
           {{ end }}
           <!-- Second, an introductive message before ToC, if it exists -->
           {{ with .Params.intro | markdownify | safeHTML }}