Implement infrastructure for detecting and handling of simultaneous edits.

lib/gollum/app.rb

@@ -176,6 +176,7 @@ module Precious
               @page         = page
               @page.version = wiki.repo.log(wiki.ref, @page.path).first
               @content      = page.text_data
+              @etag       = Digest::SHA1.hexdigest(@content)
               mustache :edit
           else
             redirect_to("/create/#{encodeURIComponent(@name)}")
@@ -278,11 +279,17 @@ module Precious
       end
 
       post '/edit/*' do
+        etag = params[:etag]        
         path      = "/#{clean_url(sanitize_empty_params(params[:path]))}"
         page_name = CGI.unescape(params[:page])
         wiki      = wiki_new
         page      = wiki.paged(page_name, path, exact = true)
+        
         return if page.nil?
+        if etag != Digest::SHA1.hexdigest(page.text_data) 
+          halt 412, 'For future use: some helpful data for resolving the conflict here.'
+        end
+        
         committer = Gollum::Committer.new(wiki, commit_message)
         commit    = { :committer => committer }
 
@@ -292,7 +299,6 @@ module Precious
         update_wiki_page(wiki, page.sidebar, params[:sidebar], commit) if params[:sidebar]
         committer.commit
 
-        redirect to("/#{page.escaped_url_path}") unless page.nil?
       end
 
 

lib/gollum/public/gollum/javascript/gollum.js.erb

@@ -367,6 +367,34 @@ $(document).ready(function() {
       window.onbeforeunload = function(){ return "Leaving will discard all edits!" };
     });
     $.GollumEditor();
+    $("#gollum-editor-submit").click( function(e) {
+      e.preventDefault();
+      // Prevent button from being clicked again
+      $(this).attr('disabled', true);
+
+      var formData = new FormData($('#gollum-editor-form').get(0));
+      var endpoint = $('#gollum-editor-form').attr("action");
+
+      $.ajax({
+        url: endpoint,
+        type: 'POST',
+        data: formData,
+        processData: false,
+        contentType: false,
+        success: function(data) {
+          window.location = window.location.href.replace(/gollum\/edit\//, '')
+        },
+        error: function(data, textStatus, errorThrown) {
+          if (data.status == 412) {
+            $('#gollum-editor-submit').attr('disabled', false)
+            alert('Someone else has modified this page while you were editing it. Please store your version on disk outside of the browser, reload this page and reapply your modifications.');
+          } else {
+            alert('Error updating page: ' + textStatus + ' ' + errorThrown);
+          }  
+        }
+      });
+      
+    });
   }
 
   if( $("#last-edit").length ) {

lib/gollum/templates/editor.mustache

@@ -1,9 +1,9 @@
 <div id="gollum-editor" data-escaped-name="{{escaped_name}}" class="{{#is_create_page}}create{{/is_create_page}}{{#is_edit_page}}edit{{/is_edit_page}} {{#allow_uploads}}uploads-allowed{{/allow_uploads}}">
 {{#is_create_page}}
-<form name="gollum-editor" action="{{create_path}}" method="post">
+<form id="gollum-editor-form" name="gollum-editor" action="{{create_path}}" method="post">
 {{/is_create_page}}
 {{#is_edit_page}}
-<form name="gollum-editor" action="{{edit_path}}/{{escaped_name}}" method="post">
+<form id="gollum-editor-form" name="gollum-editor" action="{{edit_path}}/{{escaped_name}}" method="post">
 {{/is_edit_page}}
   <fieldset id="gollum-editor-fields">
   {{#is_create_page}}
@@ -17,6 +17,7 @@
   {{/is_create_page}}
   {{#is_edit_page}}
   <input type="hidden" name="page" id="gollum-editor-page-title" value="{{page_name}}">
+  <input type="hidden" name="etag" id="gollum-editor-etag" value="{{etag}}">
   {{/is_edit_page}}
   <input type="hidden" name="path" id="gollum-editor-page-path" value="{{path}}">
   <div id="gollum-editor-function-bar">

lib/gollum/views/edit.rb

@@ -60,6 +60,9 @@ module Precious
         true
       end
 
+      def etag
+        @etag
+      end
       
       def allow_uploads
         @allow_uploads