no need for transition_url (theoretically)

Author: zkamvar

_includes/check_transition_variables.html

@@ -1,12 +1,5 @@
 {% assign date = include.need_transition_date %}
 
-{% unless site.transition_url %}
-<div class="alert alert-danger">
-  you need to specify the variable <code>transition_url</code>
-  in <code>_config.yml</code>.
-</div>
-{% endunless %}
-
 {% if date == "true" %}
 {% unless site.transition_date_prebeta %}
 <div class="alert alert-danger">

_includes/life_cycle.html

@@ -33,19 +33,23 @@
 
 
 {% comment %}
-Below we cover the 3 phases of lesson transition towards the Carpentries Workbench:
-- transition-step-1 (`transition_url` variable needed): we indicate that there
-is a new version of the lesson that is available for testing, and that it will be deprecated in the future.
-- transition-step-2 (`transition_url` and `transition_date` variables needed): we indicate that a new version of the lesson is avaiable with a deprecation date.
-- transition-step-3 (`transition_url` variable needed): the lesson is fully deprecated, and a redirect is set up to the new URL
+Below we cover the 2 phases of lesson transition towards the Carpentries Workbench:
+Variables needed:
+  - transition_date_prebeta: the date of the prebeta stage
+  - transition_date_beta: the date of the beta stage
+  - transition_date_prerelease: the date of the prerelease stage
+
+- transition-step-1: We notify that there is a snapshot of the lesson available for testing, and that it will supersede this version.
+- transition-step-2 We indicate that this version of the lesson is a snapshot and a new version of the lesson is avaiable and will supersede this version at a given date.
 {% endcomment %}
 
 {% elsif site.life_cycle == "transition-step-1" %}
 {% include check_transition_variables.html need_transition_date = 'true' %}
 
 <div class="alert alert-warning life-cycle">
   A snapshot of this lesson from {{ site.transition_date_prebeta }} is being tested on
-  <a href='https://carpentries.github.io/workbench'>The Carpentries Workbench</a>: <a href="{{ site.transition_url }}">{{ site.transition_url }}</a>.
+  <a href='https://carpentries.github.io/workbench'>The Carpentries Workbench</a>:
+  <a href="https://preview.carpentries.org/{{ repo_name }}">https://preview.carpentries.org/{{ repo_name }}</a>.
   <br>
   <b>The Workbench version of this lesson will become default on {{ site.transition_date_prerelease }}</b>.
   <button type="button" style="border: true; position: absolute; top: 10px; right: 27px; color: #383838;" class="close" data-dismiss="alert" aria-label="Close">
@@ -59,7 +63,7 @@
 <div class="alert alert-danger alert-dismissible life-cycle" role="alert">
   This lesson is a <b>snapshot from {{ site.transition_date_beta }}</b>.
   A newer version is being tested on <a href='https://carpentries.github.io/workbench'>The Carpentries Workbench</a>:
-  <a href="{{ site.transition_url }}">{{ site.transition_url }}</a>.
+  <a href="https://preview.carpentries.org/{{ repo_name }}">https://preview.carpentries.org/{{ repo_name }}</a>.
   <br>
   <b>The Workbench version of this lesson will become default on {{ site.transition_date_prerelease }}</b>.
   <button type="button" style="border: true; position: absolute; top: 10px; right: 27px; color: #383838;" class="close" data-dismiss="alert" aria-label="Close">