Let invites be declined.

app/controllers/invites_controller.rb

 class InvitesController < ApplicationController
   before_filter :member
+  skip_before_filter :authenticate_user!, only: :decline
   respond_to :html
@@ -31,6 +32,32 @@ class InvitesController < ApplicationController
     end
   end
+  def decline
+    if member.decline_invite!
+      case member.source
+      when Project
+        project = member.source
+        source = "project #{project.name_with_namespace}"
+      when Group
+        group = member.source
+        source = "group #{group.name}"
+      else
+        source = "who knows what"
+      end
+
+      path = 
+        if current_user
+          dashboard_path
+        else
+          new_user_session_path
+        end
+
+      redirect_to path, notice: "You have declined the invite to join #{source}."
+    else
+      redirect_to :back, alert: "The invite could not be declined."
+    end
+  end
+
   private
   def member

app/mailers/emails/groups.rb

@@ -27,5 +27,18 @@ module Emails
       mail(to: @group_member.created_by.notification_email,
            subject: subject("Invite accepted"))
     end
+
+    def group_invite_declined_email(group_id, invite_email, access_level, created_by_id)
+      return if created_by_id.nil?
+
+      @group = Group.find(group_id)
+      @created_by = User.find(created_by_id)
+      @access_level = access_level
+      @invite_email = invite_email
+      @target_url = group_url(@group)
+
+      mail(to: @created_by.notification_email,
+           subject: subject("Invite declined"))
+    end
   end
 end

app/mailers/emails/projects.rb

@@ -28,6 +28,19 @@ module Emails
            subject: subject("Invite accepted"))
     end
+    def project_invite_declined_email(project_id, invite_email, access_level, created_by_id)
+      return if created_by_id.nil?
+
+      @project = Project.find(project_id)
+      @created_by = User.find(created_by_id)
+      @access_level = access_level
+      @invite_email = invite_email
+      @target_url = namespace_project_url(@project.namespace, @project)
+
+      mail(to: @created_by.notification_email,
+           subject: subject("Invite declined"))
+    end
+
     def project_was_moved_email(project_id, user_id)
       @current_user = @user = User.find user_id
       @project = Project.find project_id

app/models/member.rb

@@ -76,6 +76,16 @@ class Member < ActiveRecord::Base
     saved
   end
+  def decline_invite!
+    return false unless invite?
+
+    destroyed = self.destroy
+
+    after_decline_invite if destroyed
+
+    destroyed
+  end
+
   def generate_invite_token
     raw, enc = Devise.token_generator.generate(self.class, :invite_token)
     @raw_invite_token = raw
@@ -116,6 +126,10 @@ class Member < ActiveRecord::Base
     post_create_hook
   end
+  def after_decline_invite
+    # override in subclass
+  end
+
   def system_hook_service
     SystemHooksService.new
   end

app/models/members/group_member.rb

@@ -66,4 +66,10 @@ class GroupMember < Member
     super
   end
+
+  def after_decline_invite
+    notification_service.decline_group_invite(self)
+
+    super
+  end
 end

app/models/members/project_member.rb

@@ -167,6 +167,12 @@ class ProjectMember < Member
     super
   end
+  def after_decline_invite
+    notification_service.decline_project_invite(self)
+
+    super
+  end
+
   def event_service
     EventCreateService.new
   end

app/services/notification_service.rb

@@ -173,6 +173,10 @@ class NotificationService
     mailer.project_invite_accepted_email(project_member.id)
   end
+  def decline_project_invite(project_member)
+    mailer.project_invite_declined_email(project_member.project.id, project_member.invite_email, project_member.access_level, project_member.created_by_id)
+  end
+
   def new_project_member(project_member)
     mailer.project_access_granted_email(project_member.id)
   end
@@ -189,6 +193,10 @@ class NotificationService
     mailer.group_invite_accepted_email(group_member.id)
   end
+  def decline_group_invite(group_member)
+    mailer.group_invite_declined_email(group_member.group.id, group_member.invite_email, group_member.access_level, group_member.created_by_id)
+  end
+
   def new_group_member(group_member)
     mailer.group_access_granted_email(group_member.id)
   end

app/views/invites/show.html.haml

@@ -26,3 +26,4 @@
 - else
   .actions
     = link_to "Accept invitation", accept_invite_url(@token), method: :post, class: "btn btn-success"
+    = link_to "Decline", decline_invite_url(@token), method: :post, class: "btn btn-danger prepend-left-10"

app/views/notify/group_invite_declined_email.html.haml

+%p
+  #{@invite_email}
+  has declined your invitation to join group
+  = link_to @group.name, group_url(@group)
+  as #{Gitlab::Access.options_with_owner.key(@access_level)}.
+

app/views/notify/group_invite_declined_email.text.erb

+<%= @invite_email %> has declined your invitation to join group <%= @group.name %> as <%= Gitlab::Access.options_with_owner.key(@access_level) %>.
+
+<%= group_url(@group) %>

app/views/notify/group_member_invited_email.html.haml

@@ -9,4 +9,6 @@
 %p
   = link_to 'Accept invitation', invite_url(@token)
+  or
+  = link_to 'decline', decline_invite_url(@token)

app/views/notify/group_member_invited_email.text.erb

 You have been invited <%= "by #{@group_member.created_by.name} " if @group_member.created_by %>to join group <%= @group.name %> as <%= @group_member.human_access %>.
 Accept invitation: <%= invite_url(@token) %>
+Decline invitation: <%= decline_invite_url(@token) %>

app/views/notify/project_invite_accepted_email.text.erb

-<%= @project_member.invite_email %>, now known as <%= @project_member.user.name %>, has accepted your invitation to join project <%= @group.name_with_namespace %> as <%= @project_member.human_access %>.
+<%= @project_member.invite_email %>, now known as <%= @project_member.user.name %>, has accepted your invitation to join project <%= @project.name_with_namespace %> as <%= @project_member.human_access %>.
 <%= namespace_project_url(@project.namespace, @project) %>

app/views/notify/project_invite_declined_email.html.haml

+%p
+  #{@invite_email}
+  has declined your invitation to join project
+  = link_to @project.name_with_namespace, namespace_project_url(@project.namespace, @project)
+  as #{Gitlab::Access.options_with_owner.key(@access_level)}.
+

app/views/notify/project_invite_declined_email.text.erb

+<%= @invite_email %> has declined your invitation to join project <%= @project.name_with_namespace %> as <%= Gitlab::Access.options_with_owner.key(@access_level) %>.
+
+<%= namespace_project_url(@project.namespace, @project) %>

app/views/notify/project_member_invited_email.html.haml

@@ -9,3 +9,5 @@
 %p
   = link_to 'Accept invitation', invite_url(@token)
+  or
+  = link_to 'decline', decline_invite_url(@token)

app/views/notify/project_member_invited_email.text.erb

 You have been invited <%= "by #{@project_member.created_by.name} " if @project_member.created_by %>to join project <%= @project.name_with_namespace %> as <%= @project_member.human_access %>.
 Accept invitation: <%= invite_url(@token) %>
+Decline invitation: <%= decline_invite_url(@token) %>

config/routes.rb

@@ -60,6 +60,7 @@ Gitlab::Application.routes.draw do
   resources :invites, only: [:show], constraints: { id: /[A-Za-z0-9_-]+/ } do
     member do
       post :accept
+      match :decline, via: [:get, :post]
     end
   end

spec/models/members_spec.rb

@@ -88,6 +88,23 @@ describe Member do
     end
   end
+  describe "#decline_invite!" do
+
+    let!(:member) { create(:project_member, invite_email: "user@example.com", user: nil) }
+
+    it "destroys the member" do
+      member.decline_invite!
+
+      expect(member).to be_destroyed
+    end
+
+    it "calls #after_decline_invite" do
+      expect(member).to receive(:after_decline_invite)
+
+      member.decline_invite!
+    end
+  end
+
   describe "#generate_invite_token" do
     let!(:member) { create(:project_member, invite_email: "user@example.com", user: nil) }