commit 9abd5972c4e9552833d8cc75e5f26a5a94e6829e
Author: Marius BALTEANU <marius.balteanu@zitec.com>
Date:   Tue Jul 27 02:25:27 2021 +0300

    Add setting to controll the hardbreaks behaviour from admin (#32424).

diff --git a/app/views/settings/_general.html.erb b/app/views/settings/_general.html.erb
index 23abdb3f5..a51930878 100644
--- a/app/views/settings/_general.html.erb
+++ b/app/views/settings/_general.html.erb
@@ -19,8 +19,12 @@
 
 <p><%= setting_select :protocol, [['HTTP', 'http'], ['HTTPS', 'https']] %></p>
 
-<p><%= setting_select :text_formatting, Redmine::WikiFormatting.formats_for_select, :blank => :label_none %></p>
-
+<p><%= setting_select :text_formatting, Redmine::WikiFormatting.formats_for_select, :blank => :label_none %>
+<label class="block <%= "hidden" unless Setting.text_formatting == "common_mark" %>">
+  <%= setting_check_box :text_formatting_common_mark_hardbreaks, label: false %>
+  <%= l(:setting_text_formatting_common_mark_hardbreaks) %>
+</label>
+</p>
 <p><%= setting_check_box :cache_formatted_text %></p>
 
 <p><%= setting_select :wiki_compression, [['Gzip', 'gzip']], :blank => :label_none %></p>
@@ -32,3 +36,16 @@
 
 <%= submit_tag l(:button_save) %>
 <% end %>
+
+<%= javascript_tag do %>
+  $('#settings_text_formatting').on('change', function(e){
+    const formatter = e.target.value;
+    const parent_block = document.getElementById("settings_text_formatting_common_mark_hardbreaks").parentElement;
+
+    if (formatter == "common_mark") {
+      parent_block.classList.remove('hidden');
+    } else {
+      parent_block.classList.add('hidden');
+    }
+  });
+<% end %>
diff --git a/config/locales/en.yml b/config/locales/en.yml
index e72e1bf89..ee6379b14 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -511,6 +511,7 @@ en:
   setting_project_list_defaults: Projects list defaults
   setting_twofa: Two-factor authentication
   setting_default_issue_query: Default Query
+  setting_text_formatting_common_mark_hardbreaks: "Use regular line breaks (\\n) as hardbreaks"
 
   permission_add_project: Create project
   permission_add_subprojects: Create subprojects
diff --git a/config/settings.yml b/config/settings.yml
index 7960a3f29..0248868bc 100644
--- a/config/settings.yml
+++ b/config/settings.yml
@@ -98,6 +98,8 @@ plain_text_mail:
   default: 0
 text_formatting:
   default: textile
+text_formatting_common_mark_hardbreaks:
+  default: 1
 cache_formatted_text:
   default: 0
 wiki_compression:
diff --git a/lib/redmine/wiki_formatting/common_mark/formatter.rb b/lib/redmine/wiki_formatting/common_mark/formatter.rb
index d0db8c9b8..cd0c8ba30 100644
--- a/lib/redmine/wiki_formatting/common_mark/formatter.rb
+++ b/lib/redmine/wiki_formatting/common_mark/formatter.rb
@@ -43,9 +43,14 @@ module Redmine
         # https://github.com/gjtorikian/commonmarker#render-options
         commonmarker_render_options: [
           :UNSAFE
-        ].freeze,
+        ],
       }.freeze
 
+      if Setting.text_formatting_common_mark_hardbreaks?
+        PIPELINE_CONFIG[:commonmarker_render_options].push(:HARDBREAKS)
+        PIPELINE_CONFIG[:commonmarker_render_options].freeze
+      end
+
       MarkdownPipeline = HTML::Pipeline.new [
         MarkdownFilter,
         SanitizationFilter,
diff --git a/public/stylesheets/application.css b/public/stylesheets/application.css
index e117bc1d0..0b165b447 100644
--- a/public/stylesheets/application.css
+++ b/public/stylesheets/application.css
@@ -844,6 +844,10 @@ label.block {
   float: none;
 }
 
+.tabular label.block.hidden {
+  display: none;
+}
+
 .tabular label.inline{
   font-weight: normal;
   float:none;