A simple wiki page (markdown file "_Footer.md") is used as footer for the wiki.

Github specification:
https://help.github.com/articles/creating-a-footer/

- the footer is rendered below the wiki page content.
- a direct link to edit the footer.

src/main/scala/gitbucket/core/controller/WikiController.scala

@@ -39,7 +39,8 @@ trait WikiControllerBase extends ControllerBase {
     getWikiPage(repository.owner, repository.name, "Home").map { page =>
       html.page("Home", page, getWikiPageList(repository.owner, repository.name),
         repository, hasWritePermission(repository.owner, repository.name, context.loginAccount),
-        getWikiPage(repository.owner, repository.name, "_Sidebar"))
+        getWikiPage(repository.owner, repository.name, "_Sidebar"),
+        getWikiPage(repository.owner, repository.name, "_Footer"))
     } getOrElse redirect(s"/${repository.owner}/${repository.name}/wiki/Home/_edit")
   })
   
@@ -49,7 +50,8 @@ trait WikiControllerBase extends ControllerBase {
     getWikiPage(repository.owner, repository.name, pageName).map { page =>
       html.page(pageName, page, getWikiPageList(repository.owner, repository.name),
         repository, hasWritePermission(repository.owner, repository.name, context.loginAccount),
-        getWikiPage(repository.owner, repository.name, "_Sidebar"))
+        getWikiPage(repository.owner, repository.name, "_Sidebar"),
+        getWikiPage(repository.owner, repository.name, "_Footer"))
     } getOrElse redirect(s"/${repository.owner}/${repository.name}/wiki/${StringUtil.urlEncode(pageName)}/_edit")
   })
   
@@ -203,7 +205,7 @@ trait WikiControllerBase extends ControllerBase {
       }
   }
 
-  private def notReservedPageName(value: String) = value != "_Sidebar"
+  private def notReservedPageName(value: String) = ! (Array[String]("_Sidebar","_Footer") contains value)
 
   private def conflictForNew: Constraint = new Constraint(){
     override def validate(name: String, value: String, messages: Messages): Option[String] = {

src/main/twirl/gitbucket/core/wiki/page.scala.html

@@ -3,7 +3,8 @@
   pages: List[String],
   repository: gitbucket.core.service.RepositoryService.RepositoryInfo,
   hasWritePermission: Boolean,
-  sidebar: Option[gitbucket.core.service.WikiService.WikiPageInfo])(implicit context: gitbucket.core.controller.Context)
+  sidebar: Option[gitbucket.core.service.WikiService.WikiPageInfo],
+  footer: Option[gitbucket.core.service.WikiService.WikiPageInfo])(implicit context: gitbucket.core.controller.Context)
 @import context._
 @import gitbucket.core.view.helpers._
 @import gitbucket.core.service.WikiService._
@@ -59,7 +60,7 @@
       }.getOrElse{
         @if(hasWritePermission){
           <a class="button-link" href="@url(repository)/wiki/_Sidebar/_edit" style="text-decoration: none;">
-            <div class="wiki-sidebar" style="text-align:center;">
+            <div class="wiki-sidebar-dotted" style="text-align:center;">
               <i class="octicon octicon-plus" style="font-size: 16px;"></i>
                Add a custom sidebar
             </div>
@@ -82,6 +83,25 @@
       <div class="markdown-body">
         @markdown(page.content, repository, true, false, false, false, pages)
       </div>
+      @footer.map { footerPage =>
+        <div class="wiki-sidebar wiki-footer">
+          @if(hasWritePermission){
+            <a href="@url(repository)/wiki/_Footer/_edit" style="text-decoration: none;">
+              <span class="octicon octicon-pencil" style="position: relative; float: right;"></span>
+            </a>
+          }
+          @markdown(footerPage.content, repository, true, false, false, false, pages)
+        </div>
+      }.getOrElse{
+        @if(hasWritePermission){
+          <a class="button-link" href="@url(repository)/wiki/_Footer/_edit" style="text-decoration: none;">
+            <div class="wiki-sidebar-dotted" style="text-align:center;">
+              <i class="octicon octicon-plus" style="font-size: 16px;"></i>
+               Add a custom footer
+            </div>
+          </a>
+        }
+      }
     </div>
   }
 }

src/main/webapp/assets/common/css/gitbucket.css

@@ -1195,6 +1195,22 @@ div.wiki-sidebar {
   margin-top: 20px;
 }
 
+div.wiki-sidebar-dotted {
+  background-color: white;
+  border: 1px dotted #d8d8d8;
+  padding: 4px;
+  border-bottom-left-radius: 3px;
+  border-bottom-right-radius: 3px;
+  margin-bottom: 20px;
+  margin-top: 20px;
+}
+
+div.wiki-footer {
+  margin-top: 50px;
+  background-color: #f5f5f5;
+  color: gray;
+}
+
 div.wiki-index-content {
   background-color: white;
   border: 1px solid #d8d8d8;