[FIX] mail: chatter: re-re-add the read more / less

The read more / read less in chatter has been removed in the new timeline and
then cleaned timeline introduced at cc6d2aa995.
This feature has been brought back at revision 486aab5098.
However a new cleaning removed the feature at revision 2a5f07e0b9.

This commit brings back this feature for the second time. Next one brings free
cookies.

addons/mail/models/mail_message.py

@@ -315,7 +315,7 @@ class Message(models.Model):
                 'attachment_ids': attachment_ids,
                 'tracking_value_ids': tracking_value_ids,
             })
-            body_short = tools.html_email_clean(message_dict['body'], remove=True)
+            body_short = tools.html_email_clean(message_dict['body'], shorten=True, remove=True)
             message_dict['body_short'] = body_short != message_dict['body'] and body_short or False
 
         return True

addons/mail/static/src/js/chat_manager.js

@@ -69,6 +69,7 @@ function make_message (data) {
     var msg = {
         id: data.id,
         author_id: data.author_id,
+        body_short: data.body_short || "",
         body: data.body || "",
         date: data.date,
         message_type: data.message_type,

addons/mail/static/src/js/thread.js

@@ -35,6 +35,12 @@ var Thread = Widget.extend({
             this.$('.o_thread_message').removeClass('o_thread_selected_message');
             $(event.currentTarget).toggleClass('o_thread_selected_message', !selected);
         },
+        "click span.oe_mail_expand": function (event) {
+            event.preventDefault();
+            var $source = $(event.currentTarget);
+            $source.parents('.o_thread_message_core').find('.o_mail_body_short').toggle();
+            $source.parents('.o_thread_message_core').find('.o_mail_body_long').toggle();
+        },
     },
 
     init: function (parent, options) {

addons/mail/static/src/less/thread.less

@@ -113,6 +113,10 @@
                 }
             }
 
+            .o_mail_body_long {
+                display: none;
+            }
+
             .o_mail_info {
                 margin-bottom: 2px;
                 .text-muted();

addons/mail/static/src/xml/thread.xml

@@ -109,7 +109,18 @@
                 </t>
                 <p t-if="message.subject" class="o_mail_subject">Subject: <t t-esc="message.subject"/></p>
                 <t t-if="!(message.tracking_value_ids &amp;&amp; message.tracking_value_ids.length &gt; 0)">
-                    <t t-raw="message.body"/>
+                    <t t-if="message.body_short">
+                        <div class="o_mail_body_short">
+                            <t t-raw="message.body_short"/>
+                        </div>
+                        <div class="o_mail_body_long">
+                            <t t-raw="message.body"/>
+                            <span class="oe_mail_expand"><a href="#">... read less</a></span>
+                        </div>
+                    </t>
+                    <t t-if="! message.body_short">
+                        <t t-raw="message.body"/>
+                    </t>
                 </t>
                 <t t-foreach="message.attachment_ids" t-as="attachment">
                     <t t-call="mail.Attachment"/>