Merge branch 'mia_backort' into 'master'

Backport of Multiple Assignees feature

See merge request !11089

23 files changed, 241 insertions, 105 deletions

diff --git a/app/views/issues/_issue.atom.builder b/app/views/issues/_issue.atom.builder
index 23a88448055..2ed78bb3b65 100644
--- a/app/views/issues/_issue.atom.builder
+++ b/app/views/issues/_issue.atom.builder
@@ -23,10 +23,19 @@ xml.entry do
     end
   end
 
-  if issue.assignee
+  if issue.assignees.any?
+    xml.assignees do
+      issue.assignees.each do |assignee|
+        xml.assignee do
+          xml.name assignee.name
+          xml.email assignee.public_email
+        end
+      end
+    end
+
     xml.assignee do
-      xml.name issue.assignee.name
-      xml.email issue.assignee_public_email
+      xml.name issue.assignees.first.name
+      xml.email issue.assignees.first.public_email
     end
   end
 end
diff --git a/app/views/notify/_reassigned_issuable_email.text.erb b/app/views/notify/_reassigned_issuable_email.text.erb
deleted file mode 100644
index daf20a226dd..00000000000
--- a/app/views/notify/_reassigned_issuable_email.text.erb
+++ /dev/null
@@ -1,6 +0,0 @@
-Reassigned <%= issuable.class.model_name.human.titleize %> <%= issuable.iid %>
-
-<%= url_for([issuable.project.namespace.becomes(Namespace), issuable.project, issuable, { only_path: false }]) %>
-
-Assignee changed <%= "from #{@previous_assignee.name}" if @previous_assignee -%>
- to <%= "#{issuable.assignee_id ? issuable.assignee_name : 'Unassigned'}" %>
diff --git a/app/views/notify/new_issue_email.html.haml b/app/views/notify/new_issue_email.html.haml
index c762578971a..eb5157ccac9 100644
--- a/app/views/notify/new_issue_email.html.haml
+++ b/app/views/notify/new_issue_email.html.haml
@@ -2,9 +2,9 @@
   %p.details
     #{link_to @issue.author_name, user_url(@issue.author)} created an issue:
 
-- if @issue.assignee_id.present?
+- if @issue.assignees.any?
   %p
-    Assignee: #{@issue.assignee_name}
+    Assignee: #{@issue.assignee_list}
 
 - if @issue.description
   %div
diff --git a/app/views/notify/new_issue_email.text.erb b/app/views/notify/new_issue_email.text.erb
index ca5c2f2688c..13f1ac08e94 100644
--- a/app/views/notify/new_issue_email.text.erb
+++ b/app/views/notify/new_issue_email.text.erb
@@ -2,6 +2,6 @@ New Issue was created.
 
 Issue <%= @issue.iid %>: <%= url_for(namespace_project_issue_url(@issue.project.namespace, @issue.project, @issue)) %>
 Author:    <%= @issue.author_name %>
-Assignee:  <%= @issue.assignee_name %>
+Assignee:  <%= @issue.assignee_list %>
 
 <%= @issue.description %>
diff --git a/app/views/notify/new_mention_in_issue_email.text.erb b/app/views/notify/new_mention_in_issue_email.text.erb
index 457e94b4800..f19ac3adfc7 100644
--- a/app/views/notify/new_mention_in_issue_email.text.erb
+++ b/app/views/notify/new_mention_in_issue_email.text.erb
@@ -2,6 +2,6 @@ You have been mentioned in an issue.
 
 Issue <%= @issue.iid %>: <%= url_for(namespace_project_issue_url(@issue.project.namespace, @issue.project, @issue)) %>
 Author:    <%= @issue.author_name %>
-Assignee:  <%= @issue.assignee_name %>
+Assignee:  <%= @issue.assignee_list %>
 
 <%= @issue.description %>
diff --git a/app/views/notify/reassigned_issue_email.html.haml b/app/views/notify/reassigned_issue_email.html.haml
index 498ba8b8365..ee2f40e1683 100644
--- a/app/views/notify/reassigned_issue_email.html.haml
+++ b/app/views/notify/reassigned_issue_email.html.haml
@@ -1 +1,10 @@
-= render 'reassigned_issuable_email', issuable: @issue
+%p
+  Assignee changed
+  - if @previous_assignees.any?
+    from
+    %strong= @previous_assignees.map(&:name).to_sentence
+  to
+  - if @issue.assignees.any?
+    %strong= @issue.assignee_list
+  - else
+    %strong Unassigned
diff --git a/app/views/notify/reassigned_issue_email.text.erb b/app/views/notify/reassigned_issue_email.text.erb
index 710253be984..6c357f1074a 100644
--- a/app/views/notify/reassigned_issue_email.text.erb
+++ b/app/views/notify/reassigned_issue_email.text.erb
@@ -1 +1,6 @@
-<%= render 'reassigned_issuable_email', issuable: @issue %>
+Reassigned Issue <%= @issue.iid %>
+
+<%= url_for([@issue.project.namespace.becomes(Namespace), @issue.project, @issue, { only_path: false }]) %>
+
+Assignee changed <%= "from #{@previous_assignees.map(&:name).to_sentence}" if @previous_assignees.any? -%>
+ to <%= "#{@issue.assignees.any? ? @issue.assignee_list : 'Unassigned'}" %>
diff --git a/app/views/notify/reassigned_merge_request_email.html.haml b/app/views/notify/reassigned_merge_request_email.html.haml
index 2a650130f59..841df872857 100644
--- a/app/views/notify/reassigned_merge_request_email.html.haml
+++ b/app/views/notify/reassigned_merge_request_email.html.haml
@@ -1 +1,9 @@
-= render 'reassigned_issuable_email', issuable: @merge_request
+Reassigned Merge Request #{ @merge_request.iid }
+
+= url_for([@merge_request.project.namespace.becomes(Namespace), @merge_request.project, @merge_request, { only_path: false }])
+
+Assignee changed
+- if @previous_assignee
+  from #{@previous_assignee.name}
+to
+= @merge_request.assignee_id ? @merge_request.assignee_name : 'Unassigned'
diff --git a/app/views/notify/reassigned_merge_request_email.text.erb b/app/views/notify/reassigned_merge_request_email.text.erb
index b5b4f1ff99a..998a40fefde 100644
--- a/app/views/notify/reassigned_merge_request_email.text.erb
+++ b/app/views/notify/reassigned_merge_request_email.text.erb
@@ -1 +1,6 @@
-<%= render 'reassigned_issuable_email', issuable: @merge_request %>
+Reassigned Merge Request <%= @merge_request.iid %>
+
+<%= url_for([@merge_request.project.namespace.becomes(Namespace), @merge_request.project, @merge_request, { only_path: false }]) %>
+
+Assignee changed <%= "from #{@previous_assignee.name}" if @previous_assignee -%>
+ to <%= "#{@merge_request.assignee_id ? @merge_request.assignee_name : 'Unassigned'}" %>
diff --git a/app/views/projects/boards/components/sidebar/_assignee.html.haml b/app/views/projects/boards/components/sidebar/_assignee.html.haml
index 0f424334521..642da679f97 100644
--- a/app/views/projects/boards/components/sidebar/_assignee.html.haml
+++ b/app/views/projects/boards/components/sidebar/_assignee.html.haml
@@ -1,40 +1,28 @@
-.block.assignee
-  .title.hide-collapsed
-    Assignee
-    - if can?(current_user, :admin_issue, @project)
-      = icon("spinner spin", class: "block-loading")
-      = link_to "Edit", "#", class: "edit-link pull-right"
-  .value.hide-collapsed
-    %span.assign-yourself.no-value{ "v-if" => "!issue.assignee" }
-      No assignee
-      - if can?(current_user, :admin_issue, @project)
-        \-
-        %a.js-assign-yourself{ href: "#" }
-          assign yourself
-    %a.author_link.bold{ ":href" => "'#{root_url}' + issue.assignee.username",
-      "v-if" => "issue.assignee" }
-      %img.avatar.avatar-inline.s32{ ":src" => "issue.assignee.avatar",
-        width: "32", alt: "Avatar" }
-      %span.author
-        {{ issue.assignee.name }}
-      %span.username
-        = precede "@" do
-          {{ issue.assignee.username }}
+.block.assignee{ ref: "assigneeBlock" }
+  %template{ "v-if" => "issue.assignees" }
+    %assignee-title{ ":number-of-assignees" => "issue.assignees.length",
+      ":loading" => "loadingAssignees",
+      ":editable" => can?(current_user, :admin_issue, @project) }
+    %assignees.value{ "root-path" => "#{root_url}",
+      ":users" => "issue.assignees",
+      ":editable" => can?(current_user, :admin_issue, @project),
+      "@assign-self" => "assignSelf" }
+
   - if can?(current_user, :admin_issue, @project)
     .selectbox.hide-collapsed
       %input{ type: "hidden",
-        name: "issue[assignee_id]",
-        id: "issue_assignee_id",
-        ":value" => "issue.assignee.id",
-        "v-if" => "issue.assignee" }
+        name: "issue[assignee_ids][]",
+        ":value" => "assignee.id",
+        "v-if" => "issue.assignees",
+        "v-for" => "assignee in issue.assignees" }
       .dropdown
-        %button.dropdown-menu-toggle.js-user-search.js-author-search.js-issue-board-sidebar{ type: "button", data: { toggle: "dropdown", field_name: "issue[assignee_id]", first_user: (current_user.username if current_user), current_user: "true", project_id: @project.id, null_user: "true", null_user_default: "true" },
+        %button.dropdown-menu-toggle.js-user-search.js-author-search.js-multiselect.js-save-user-data.js-issue-board-sidebar{ type: "button", ref: "assigneeDropdown", data: { toggle: "dropdown", field_name: "issue[assignee_ids][]", first_user: (current_user.username if current_user), current_user: "true", project_id: @project.id, null_user: "true", multi_select: "true", 'max-select' => 1, dropdown: { header: 'Assignee' } },
           ":data-issuable-id" => "issue.id",
           ":data-selected" => "assigneeId",
           ":data-issue-update" => "'#{namespace_project_issues_path(@project.namespace, @project)}/' + issue.id + '.json'" }
           Select assignee
           = icon("chevron-down")
-        .dropdown-menu.dropdown-menu-user.dropdown-menu-selectable.dropdown-menu-author
+        .dropdown-menu.dropdown-select.dropdown-menu-user.dropdown-menu-selectable.dropdown-menu-author
           = dropdown_title("Assign to")
           = dropdown_filter("Search users")
           = dropdown_content
diff --git a/app/views/projects/issues/_issue.html.haml b/app/views/projects/issues/_issue.html.haml
index 0e3902c066a..c184e0e0022 100644
--- a/app/views/projects/issues/_issue.html.haml
+++ b/app/views/projects/issues/_issue.html.haml
@@ -13,9 +13,9 @@
             %li
               CLOSED
 
-          - if issue.assignee
+          - if issue.assignees.any?
             %li
-              = link_to_member(@project, issue.assignee, name: false, title: "Assigned to :name")
+              = render 'shared/issuable/assignees', project: @project, issue: issue
 
           = render 'shared/issuable_meta_data', issuable: issue
 
diff --git a/app/views/projects/protected_branches/_create_protected_branch.html.haml b/app/views/projects/protected_branches/_create_protected_branch.html.haml
index b8e885b4d9a..99bc2516366 100644
--- a/app/views/projects/protected_branches/_create_protected_branch.html.haml
+++ b/app/views/projects/protected_branches/_create_protected_branch.html.haml
@@ -25,7 +25,7 @@
             .merge_access_levels-container
               = dropdown_tag('Select',
                              options: { toggle_class: 'js-allowed-to-merge wide',
-                             dropdown_class: 'dropdown-menu-selectable',
+                             dropdown_class: 'dropdown-menu-selectable capitalize-header',
                              data: { field_name: 'protected_branch[merge_access_levels_attributes][0][access_level]', input_id: 'merge_access_levels_attributes' }})
         .form-group
           %label.col-md-2.text-right{ for: 'push_access_levels_attributes' }
@@ -34,7 +34,7 @@
             .push_access_levels-container
               = dropdown_tag('Select',
                              options: { toggle_class: 'js-allowed-to-push wide',
-                             dropdown_class: 'dropdown-menu-selectable',
+                             dropdown_class: 'dropdown-menu-selectable capitalize-header',
                              data: { field_name: 'protected_branch[push_access_levels_attributes][0][access_level]', input_id: 'push_access_levels_attributes' }})
 
     .panel-footer
diff --git a/app/views/projects/protected_branches/_update_protected_branch.html.haml b/app/views/projects/protected_branches/_update_protected_branch.html.haml
index d6044aacaec..c61b2951e1e 100644
--- a/app/views/projects/protected_branches/_update_protected_branch.html.haml
+++ b/app/views/projects/protected_branches/_update_protected_branch.html.haml
@@ -1,10 +1,10 @@
 %td
   = hidden_field_tag "allowed_to_merge_#{protected_branch.id}", protected_branch.merge_access_levels.first.access_level
   = dropdown_tag( (protected_branch.merge_access_levels.first.humanize || 'Select') ,
-                 options: { toggle_class: 'js-allowed-to-merge', dropdown_class: 'dropdown-menu-selectable js-allowed-to-merge-container',
+                 options: { toggle_class: 'js-allowed-to-merge', dropdown_class: 'dropdown-menu-selectable js-allowed-to-merge-container capitalize-header',
                  data: { field_name: "allowed_to_merge_#{protected_branch.id}", access_level_id: protected_branch.merge_access_levels.first.id }})
 %td
   = hidden_field_tag "allowed_to_push_#{protected_branch.id}", protected_branch.push_access_levels.first.access_level
   = dropdown_tag( (protected_branch.push_access_levels.first.humanize || 'Select') ,
-                 options: { toggle_class: 'js-allowed-to-push', dropdown_class: 'dropdown-menu-selectable js-allowed-to-push-container',
+                 options: { toggle_class: 'js-allowed-to-push', dropdown_class: 'dropdown-menu-selectable js-allowed-to-push-container capitalize-header',
                  data: { field_name: "allowed_to_push_#{protected_branch.id}", access_level_id: protected_branch.push_access_levels.first.id }})
diff --git a/app/views/projects/protected_tags/_dropdown.html.haml b/app/views/projects/protected_tags/_dropdown.html.haml
index 74851519077..c50515cfe06 100644
--- a/app/views/projects/protected_tags/_dropdown.html.haml
+++ b/app/views/projects/protected_tags/_dropdown.html.haml
@@ -2,7 +2,7 @@
 
 = dropdown_tag('Select tag or create wildcard',
                options: { toggle_class: 'js-protected-tag-select js-filter-submit wide',
-                          filter: true, dropdown_class: "dropdown-menu-selectable", placeholder: "Search protected tag",
+                          filter: true, dropdown_class: "dropdown-menu-selectable  capitalize-header", placeholder: "Search protected tag",
                           footer_content: true,
                           data: { show_no: true, show_any: true, show_upcoming: true,
                                   selected: params[:protected_tag_name],
diff --git a/app/views/projects/protected_tags/_update_protected_tag.haml b/app/views/projects/protected_tags/_update_protected_tag.haml
index 62823bee46e..cc80bd04dd0 100644
--- a/app/views/projects/protected_tags/_update_protected_tag.haml
+++ b/app/views/projects/protected_tags/_update_protected_tag.haml
@@ -1,5 +1,5 @@
 %td
   = hidden_field_tag "allowed_to_create_#{protected_tag.id}", protected_tag.create_access_levels.first.access_level
   = dropdown_tag( (protected_tag.create_access_levels.first.humanize || 'Select') ,
-                 options: { toggle_class: 'js-allowed-to-create', dropdown_class: 'dropdown-menu-selectable js-allowed-to-create-container',
+                 options: { toggle_class: 'js-allowed-to-create', dropdown_class: 'dropdown-menu-selectable capitalize-header js-allowed-to-create-container',
                  data: { field_name: "allowed_to_create_#{protected_tag.id}", access_level_id: protected_tag.create_access_levels.first.id }})
diff --git a/app/views/shared/issuable/_assignees.html.haml b/app/views/shared/issuable/_assignees.html.haml
new file mode 100644
index 00000000000..36bbb1148d4
--- /dev/null
+++ b/app/views/shared/issuable/_assignees.html.haml
@@ -0,0 +1,15 @@
+- max_render = 3
+- max = [max_render, issue.assignees.length].min
+
+- issue.assignees.each_with_index do |assignee, index|
+  - if index < max
+    = link_to_member(@project, assignee, name: false, title: "Assigned to :name")
+
+- if issue.assignees.length > max_render
+  - counter = issue.assignees.length - max_render
+
+  %span{ class: 'avatar-counter has-tooltip', data: { container: 'body', placement: 'bottom', 'line-type' => 'old', 'original-title' => "+#{counter} more assignees" } }
+    - if counter < 99
+      = "+#{counter}"
+    - else
+      99+
diff --git a/app/views/shared/issuable/_participants.html.haml b/app/views/shared/issuable/_participants.html.haml
index 171da899937..db407363a09 100644
--- a/app/views/shared/issuable/_participants.html.haml
+++ b/app/views/shared/issuable/_participants.html.haml
@@ -12,9 +12,9 @@
     - participants.each do |participant|
       .participants-author.js-participants-author
         = link_to_member(@project, participant, name: false, size: 24)
-    - if participants_extra > 0
-      .participants-more
-        %a.js-participants-more{ href: "#", data: { original_text: "+ #{participants_size - 7} more", less_text: "- show less" } }
-          + #{participants_extra} more
+  - if participants_extra > 0
+    .hide-collapsed.participants-more
+      %a.js-participants-more{ href: "#", data: { original_text: "+ #{participants_size - 7} more", less_text: "- show less" } }
+        + #{participants_extra} more
 :javascript
   IssuableContext.prototype.PARTICIPANTS_ROW_COUNT = #{participants_row};
diff --git a/app/views/shared/issuable/_search_bar.html.haml b/app/views/shared/issuable/_search_bar.html.haml
index b6fce5e3cd4..f7b87171573 100644
--- a/app/views/shared/issuable/_search_bar.html.haml
+++ b/app/views/shared/issuable/_search_bar.html.haml
@@ -124,8 +124,13 @@
                 %li
                   %a{ href: "#", data: { id: "close" } } Closed
           .filter-item.inline
+            - if type == :issues
+              - field_name = "update[assignee_ids][]"
+            - else
+              - field_name = "update[assignee_id]"
+
             = dropdown_tag("Assignee", options: { toggle_class: "js-user-search js-update-assignee js-filter-submit js-filter-bulk-update", title: "Assign to", filter: true, dropdown_class: "dropdown-menu-user dropdown-menu-selectable",
-              placeholder: "Search authors", data: { first_user: (current_user.username if current_user), null_user: true, current_user: true, project_id: @project.id, field_name: "update[assignee_id]", default_label: "Assignee" } })
+              placeholder: "Search authors", data: { first_user: (current_user.username if current_user), null_user: true, current_user: true, project_id: @project.id, field_name: field_name } })
           .filter-item.inline
             = dropdown_tag("Milestone", options: { title: "Assign milestone", toggle_class: 'js-milestone-select js-extra-options js-filter-submit js-filter-bulk-update', filter: true, dropdown_class: "dropdown-menu-selectable dropdown-menu-milestone", placeholder: "Search milestones", data: { show_no: true, field_name: "update[milestone_id]", project_id: @project.id, milestones: namespace_project_milestones_path(@project.namespace, @project, :json), use_id: true, default_label: "Milestone" } })
           .filter-item.inline.labels-filter
diff --git a/app/views/shared/issuable/_sidebar.html.haml b/app/views/shared/issuable/_sidebar.html.haml
index bc638e994f3..44e624c15a7 100644
--- a/app/views/shared/issuable/_sidebar.html.haml
+++ b/app/views/shared/issuable/_sidebar.html.haml
@@ -1,10 +1,10 @@
 - todo = issuable_todo(issuable)
 - content_for :page_specific_javascripts do
   = page_specific_javascript_bundle_tag('common_vue')
-  = page_specific_javascript_bundle_tag('issuable')
+  = page_specific_javascript_bundle_tag('sidebar')
 
 %aside.right-sidebar.js-right-sidebar{ data: { "offset-top" => "102", "spy" => "affix" }, class: sidebar_gutter_collapsed_class, 'aria-live' => 'polite' }
-  .issuable-sidebar
+  .issuable-sidebar{ data: { endpoint: "#{issuable_json_path(issuable)}" } }
     - can_edit_issuable = can?(current_user, :"admin_#{issuable.to_ability_name}", @project)
     .block.issuable-sidebar-header
       - if current_user
@@ -20,36 +20,55 @@
         .block.todo.hide-expanded
           = render "shared/issuable/sidebar_todo", todo: todo, issuable: issuable, is_collapsed: true
       .block.assignee
-        .sidebar-collapsed-icon.sidebar-collapsed-user{ data: { toggle: "tooltip", placement: "left", container: "body" }, title: (issuable.assignee.name if issuable.assignee) }
-          - if issuable.assignee
-            = link_to_member(@project, issuable.assignee, size: 24)
-          - else
-            = icon('user', 'aria-hidden': 'true')
-        .title.hide-collapsed
-          Assignee
-          = icon('spinner spin', class: 'hidden block-loading', 'aria-hidden': 'true')
-          - if can_edit_issuable
-            = link_to 'Edit', '#', class: 'edit-link pull-right'
-        .value.hide-collapsed
-          - if issuable.assignee
-            = link_to_member(@project, issuable.assignee, size: 32, extra_class: 'bold') do
-              - if issuable.instance_of?(MergeRequest) && !issuable.can_be_merged_by?(issuable.assignee)
-                %span.pull-right.cannot-be-merged{ data: { toggle: 'tooltip', placement: 'left' }, title: 'Not allowed to merge' }
-                  = icon('exclamation-triangle', 'aria-hidden': 'true')
-              %span.username
-                = issuable.assignee.to_reference
-          - else
-            %span.assign-yourself.no-value
-              No assignee
-              - if can_edit_issuable
-                \-
-                %a.js-assign-yourself{ href: '#' }
-                  assign yourself
+        - if issuable.instance_of?(Issue)
+          #js-vue-sidebar-assignees{ data: { field: "#{issuable.to_ability_name}[assignee_ids]" } }
+        - else
+          .sidebar-collapsed-icon.sidebar-collapsed-user{ data: { toggle: "tooltip", placement: "left", container: "body" }, title: (issuable.assignee.name if issuable.assignee) }
+            - if issuable.assignee
+              = link_to_member(@project, issuable.assignee, size: 24)
+            - else
+              = icon('user', 'aria-hidden': 'true')
+          .title.hide-collapsed
+            Assignee
+            = icon('spinner spin', class: 'hidden block-loading', 'aria-hidden': 'true')
+            - if can_edit_issuable
+              = link_to 'Edit', '#', class: 'edit-link pull-right'
+          .value.hide-collapsed
+            - if issuable.assignee
+              = link_to_member(@project, issuable.assignee, size: 32, extra_class: 'bold') do
+                - if issuable.instance_of?(MergeRequest) && !issuable.can_be_merged_by?(issuable.assignee)
+                  %span.pull-right.cannot-be-merged{ data: { toggle: 'tooltip', placement: 'left' }, title: 'Not allowed to merge' }
+                    = icon('exclamation-triangle', 'aria-hidden': 'true')
+                %span.username
+                  = issuable.assignee.to_reference
+            - else
+              %span.assign-yourself.no-value
+                No assignee
+                - if can_edit_issuable
+                  \-
+                  %a.js-assign-yourself{ href: '#' }
+                    assign yourself
 
         .selectbox.hide-collapsed
-          = f.hidden_field 'assignee_id', value: issuable.assignee_id, id: 'issue_assignee_id'
-          = dropdown_tag('Select assignee', options: { toggle_class: 'js-user-search js-author-search', title: 'Assign to', filter: true, dropdown_class: 'dropdown-menu-user dropdown-menu-selectable dropdown-menu-author', placeholder: 'Search users', data: { first_user: (current_user.username if current_user), current_user: true, project_id: (@project.id if @project), author_id: issuable.author_id, field_name: "#{issuable.to_ability_name}[assignee_id]", issue_update: issuable_json_path(issuable), ability_name: issuable.to_ability_name, null_user: true, null_user_default: true, selected: issuable.assignee_id } })
+          - issuable.assignees.each do |assignee|
+            = hidden_field_tag "#{issuable.to_ability_name}[assignee_ids][]", assignee.id, id: nil
 
+          - options = { toggle_class: 'js-user-search js-author-search', title: 'Assign to', filter: true, dropdown_class: 'dropdown-menu-user dropdown-menu-selectable dropdown-menu-author', placeholder: 'Search users', data: { first_user: (current_user.username if current_user), current_user: true, project_id: (@project.id if @project), author_id: issuable.author_id, field_name: "#{issuable.to_ability_name}[assignee_ids][]", issue_update: issuable_json_path(issuable), ability_name: issuable.to_ability_name, null_user: true } }
+
+          - if issuable.instance_of?(Issue)
+            - if issuable.assignees.length == 0
+              = hidden_field_tag "#{issuable.to_ability_name}[assignee_ids][]", 0, id: nil
+            - title = 'Select assignee'
+            - options[:toggle_class] += ' js-multiselect js-save-user-data'
+            - options[:data][:field_name] = "#{issuable.to_ability_name}[assignee_ids][]"
+            - options[:data][:multi_select] = true
+            - options[:data]['dropdown-title'] = title
+            - options[:data]['dropdown-header'] = 'Assignee'
+            - options[:data]['max-select'] = 1
+          - else
+            - title = 'Select assignee'
+
+          = dropdown_tag(title, options: options)
       .block.milestone
         .sidebar-collapsed-icon
           = icon('clock-o', 'aria-hidden': 'true')
@@ -75,11 +94,10 @@
           = dropdown_tag('Milestone', options: { title: 'Assign milestone', toggle_class: 'js-milestone-select js-extra-options', filter: true, dropdown_class: 'dropdown-menu-selectable', placeholder: 'Search milestones', data: { show_no: true, field_name: "#{issuable.to_ability_name}[milestone_id]", project_id: @project.id, issuable_id: issuable.id, milestones: namespace_project_milestones_path(@project.namespace, @project, :json), ability_name: issuable.to_ability_name, issue_update: issuable_json_path(issuable), use_id: true }})
       - if issuable.has_attribute?(:time_estimate)
         #issuable-time-tracker.block
-          %issuable-time-tracker{ ':time_estimate' => 'issuable.time_estimate', ':time_spent' => 'issuable.total_time_spent', ':human_time_estimate' => 'issuable.human_time_estimate', ':human_time_spent' => 'issuable.human_total_time_spent', 'docs-url' => help_page_path('workflow/time_tracking.md') }
-            // Fallback while content is loading
-            .title.hide-collapsed
-              Time tracking
-              = icon('spinner spin', 'aria-hidden': 'true')
+          // Fallback while content is loading
+          .title.hide-collapsed
+            Time tracking
+            = icon('spinner spin', 'aria-hidden': 'true')
       - if issuable.has_attribute?(:due_date)
         .block.due_date
           .sidebar-collapsed-icon
@@ -169,8 +187,13 @@
           = clipboard_button(text: project_ref, title: "Copy reference to clipboard", placement: "left")
 
     :javascript
-      gl.IssuableResource = new gl.SubbableResource('#{issuable_json_path(issuable)}');
-      new gl.IssuableTimeTracking("#{escape_javascript(serialize_issuable(issuable))}");
+      gl.sidebarOptions = {
+        endpoint: "#{issuable_json_path(issuable)}",
+        editable: #{can_edit_issuable ? true : false},
+        currentUser: #{current_user.to_json(only: [:username, :id, :name], methods: :avatar_url)},
+        rootPath: "#{root_path}"
+      };
+
       new MilestoneSelect('{"full_path":"#{@project.full_path}"}');
       new LabelsSelect();
       new IssuableContext('#{escape_javascript(current_user.to_json(only: [:username, :id, :name]))}');
diff --git a/app/views/shared/issuable/form/_issue_assignee.html.haml b/app/views/shared/issuable/form/_issue_assignee.html.haml
new file mode 100644
index 00000000000..c33474ac3b4
--- /dev/null
+++ b/app/views/shared/issuable/form/_issue_assignee.html.haml
@@ -0,0 +1,30 @@
+- issue = issuable
+.block.assignee
+  .sidebar-collapsed-icon.sidebar-collapsed-user{ data: { toggle: "tooltip", placement: "left", container: "body" }, title: (issuable.assignee_list) }
+    - if issue.assignees.any?
+      - issue.assignees.each do |assignee|
+        = link_to_member(@project, assignee, size: 24)
+    - else
+      = icon('user', 'aria-hidden': 'true')
+  .title.hide-collapsed
+    Assignee
+    = icon('spinner spin', class: 'hidden block-loading', 'aria-hidden': 'true')
+    - if can_edit_issuable
+      = link_to 'Edit', '#', class: 'edit-link pull-right'
+  .value.hide-collapsed
+    - if issue.assignees.any?
+      - issue.assignees.each do |assignee|
+        = link_to_member(@project, assignee, size: 32, extra_class: 'bold') do
+          %span.username
+            = assignee.to_reference
+    - else
+      %span.assign-yourself.no-value
+        No assignee
+        - if can_edit_issuable
+          \-
+          %a.js-assign-yourself{ href: '#' }
+            assign yourself
+
+  .selectbox.hide-collapsed
+    = f.hidden_field 'assignee_ids', value: issuable.assignee_ids, id: 'issue_assignee_ids'
+    = dropdown_tag('Select assignee', options: { toggle_class: 'js-user-search js-author-search', title: 'Assign to', filter: true, dropdown_class: 'dropdown-menu-user dropdown-menu-selectable dropdown-menu-author', placeholder: 'Search users', data: { first_user: (current_user.username if current_user), current_user: true, project_id: (@project.id if @project), author_id: issuable.author_id, field_name: "#{issuable.to_ability_name}[assignee_id]", issue_update: issuable_json_path(issuable), ability_name: issuable.to_ability_name, null_user: true } })
diff --git a/app/views/shared/issuable/form/_merge_request_assignee.html.haml b/app/views/shared/issuable/form/_merge_request_assignee.html.haml
new file mode 100644
index 00000000000..18011d528a0
--- /dev/null
+++ b/app/views/shared/issuable/form/_merge_request_assignee.html.haml
@@ -0,0 +1,31 @@
+- merge_request = issuable
+.block.assignee
+  .sidebar-collapsed-icon.sidebar-collapsed-user{ data: { toggle: "tooltip", placement: "left", container: "body" }, title: (merge_request.assignee.name if merge_request.assignee) }
+    - if merge_request.assignee
+      = link_to_member(@project, merge_request.assignee, size: 24)
+    - else
+      = icon('user', 'aria-hidden': 'true')
+  .title.hide-collapsed
+    Assignee
+    = icon('spinner spin', class: 'hidden block-loading', 'aria-hidden': 'true')
+    - if can_edit_issuable
+      = link_to 'Edit', '#', class: 'edit-link pull-right'
+  .value.hide-collapsed
+    - if merge_request.assignee
+      = link_to_member(@project, merge_request.assignee, size: 32, extra_class: 'bold') do
+        - unless merge_request.can_be_merged_by?(merge_request.assignee)
+          %span.pull-right.cannot-be-merged{ data: { toggle: 'tooltip', placement: 'left' }, title: 'Not allowed to merge' }
+            = icon('exclamation-triangle', 'aria-hidden': 'true')
+        %span.username
+          = merge_request.assignee.to_reference
+    - else
+      %span.assign-yourself.no-value
+        No assignee
+        - if can_edit_issuable
+          \-
+          %a.js-assign-yourself{ href: '#' }
+            assign yourself
+
+  .selectbox.hide-collapsed
+    = f.hidden_field 'assignee_id', value: merge_request.assignee_id, id: 'issue_assignee_id'
+    = dropdown_tag('Select assignee', options: { toggle_class: 'js-user-search js-author-search', title: 'Assign to', filter: true, dropdown_class: 'dropdown-menu-user dropdown-menu-selectable dropdown-menu-author', placeholder: 'Search users', data: { first_user: (current_user.username if current_user), current_user: true, project_id: @project&.id, author_id: merge_request.author_id, field_name: 'merge_request[assignee_id]', issue_update: issuable_json_path(merge_request), ability_name: 'merge_request', null_user: true } })
diff --git a/app/views/shared/issuable/form/_metadata.html.haml b/app/views/shared/issuable/form/_metadata.html.haml
index 9dbfedb84f1..9281a515744 100644
--- a/app/views/shared/issuable/form/_metadata.html.haml
+++ b/app/views/shared/issuable/form/_metadata.html.haml
@@ -10,13 +10,27 @@
 .row
   %div{ class: (has_due_date ? "col-lg-6" : "col-sm-12") }
     .form-group.issue-assignee
-      = form.label :assignee_id, "Assignee", class: "control-label #{"col-lg-4" if has_due_date}"
-      .col-sm-10{ class: ("col-lg-8" if has_due_date) }
-        .issuable-form-select-holder
-          = form.hidden_field :assignee_id
-          = dropdown_tag(user_dropdown_label(issuable.assignee_id, "Assignee"), options: { toggle_class: "js-dropdown-keep-input js-user-search js-issuable-form-dropdown js-assignee-search", title: "Select assignee", filter: true, dropdown_class: "dropdown-menu-user dropdown-menu-selectable dropdown-menu-assignee js-filter-submit",
-            placeholder: "Search assignee", data: { first_user: current_user.try(:username), null_user: true, current_user: true, project_id: issuable.project.try(:id), selected: issuable.assignee_id, field_name: "#{issuable.class.model_name.param_key}[assignee_id]", default_label: "Assignee"} })
-        = link_to 'Assign to me', '#', class: "assign-to-me-link #{'hide' if issuable.assignee_id == current_user.id}"
+      - if issuable.is_a?(Issue)
+        = form.label :assignee_ids, "Assignee", class: "control-label #{"col-lg-4" if has_due_date}"
+        .col-sm-10{ class: ("col-lg-8" if has_due_date) }
+          .issuable-form-select-holder.selectbox
+            - issuable.assignees.each do |assignee|
+              = hidden_field_tag "#{issuable.to_ability_name}[assignee_ids][]", assignee.id, id: nil, data: { meta: assignee.name }
+
+            - if issuable.assignees.length === 0
+              = hidden_field_tag "#{issuable.to_ability_name}[assignee_ids][]", 0, id: nil, data: { meta: '' }
+
+            = dropdown_tag(users_dropdown_label(issuable.assignees), options: issue_dropdown_options(issuable,false))
+          = link_to 'Assign to me', '#', class: "assign-to-me-link #{'hide' if issuable.assignees.include?(current_user)}"
+      - else
+        = form.label :assignee_id, "Assignee", class: "control-label #{"col-lg-4" if has_due_date}"
+        .col-sm-10{ class: ("col-lg-8" if has_due_date) }
+          .issuable-form-select-holder
+            = form.hidden_field :assignee_id
+
+            = dropdown_tag(user_dropdown_label(issuable.assignee_id, "Assignee"), options: { toggle_class: "js-dropdown-keep-input js-user-search js-issuable-form-dropdown js-assignee-search", title: "Select assignee", filter: true, dropdown_class: "dropdown-menu-user dropdown-menu-selectable dropdown-menu-assignee js-filter-submit",
+              placeholder: "Search assignee", data: { first_user: current_user.try(:username), null_user: true, current_user: true, project_id: issuable.project.try(:id), selected: issuable.assignee_id, field_name: "#{issuable.class.model_name.param_key}[assignee_id]", default_label: "Assignee"} })
+          = link_to 'Assign to me', '#', class: "assign-to-me-link #{'hide' if issuable.assignee_id == current_user.id}"
     .form-group.issue-milestone
       = form.label :milestone_id, "Milestone", class: "control-label #{"col-lg-4" if has_due_date}"
       .col-sm-10{ class: ("col-lg-8" if has_due_date) }
diff --git a/app/views/shared/milestones/_issuable.html.haml b/app/views/shared/milestones/_issuable.html.haml
index 5247d6a51e6..22547a30cdf 100644
--- a/app/views/shared/milestones/_issuable.html.haml
+++ b/app/views/shared/milestones/_issuable.html.haml
@@ -1,7 +1,7 @@
 -# @project is present when viewing Project's milestone
 - project = @project || issuable.project
 - namespace = @project_namespace || project.namespace.becomes(Namespace)
-- assignee = issuable.assignee
+- assignees = issuable.assignees
 - issuable_type = issuable.class.table_name
 - base_url_args = [namespace, project]
 - issuable_type_args = base_url_args + [issuable_type]
@@ -26,7 +26,7 @@
         - render_colored_label(label)
 
     %span.assignee-icon
-      - if assignee
-        = link_to polymorphic_path(issuable_type_args, { milestone_title: @milestone.title, assignee_id: issuable.assignee_id, state: 'all' }),
+      - assignees.each do |assignee|
+        = link_to polymorphic_path(base_url_args, { milestone_title: @milestone.title, assignee_id: assignee.id, state: 'all' }),
                   class: 'has-tooltip', title: "Assigned to #{assignee.name}", data: { container: 'body' } do
-          - image_tag(avatar_icon(issuable.assignee, 16), class: "avatar s16", alt: '')
+          - image_tag(avatar_icon(assignee, 16), class: "avatar s16", alt: '')