\#to_branch_name now uses the iid as postfix

Given the branch name 'mep-mep' with an iid being 1,
the current way, master's way, would yield a branch name of
1-mep-mep. The problem for larger projects however would be that
a developer might forget what iid the issue was.

When this developer would try to tab complete it would:
- Or result in 20+ branches possibly
- Or start with the wrong digit, try again with digit++
  - Would see 20 branches, repeat

Thus the obvious way of solving this is letting the dev tab complete
on the issue title, which is easier to remember.

app/models/issue.rb

@@ -106,9 +106,8 @@ class Issue < ActiveRecord::Base
 
   def related_branches
     return [] if self.project.empty_repo?
-    self.project.repository.branch_names.select do |branch|
+    
-      branch =~ /\A#{iid}-(?!\d+-stable)/i
+    self.project.repository.branch_names.select { |branch| branch.end_with?("-#{iid}") }
-    end
   end
 
   # Reset issue events cache
@@ -139,7 +138,7 @@ class Issue < ActiveRecord::Base
   end
 
   def to_branch_name
-    "#{iid}-#{title.parameterize}"
+    "#{title.parameterize}-#{iid}"
   end
 
   def can_be_worked_on?(current_user)

app/services/merge_requests/build_service.rb

@@ -51,7 +51,7 @@ module MergeRequests
       # be interpreted as the use wants to close that issue on this project
       # Pattern example: 112-fix-mep-mep
       # Will lead to appending `Closes #112` to the description
-      if match = merge_request.source_branch.match(/\A(\d+)-/)
+      if match = merge_request.source_branch.match(/-(\d+)\z/)
         iid = match[1]
         closes_issue = "Closes ##{iid}"
 

app/services/system_note_service.rb

@@ -210,7 +210,7 @@ class SystemNoteService
   # Called when a branch is created from the 'new branch' button on a issue
   # Example note text:
   #
-  #   "Started branch `201-issue-branch-button`"
+  #   "Started branch `issue-branch-button-201`"
   def self.new_issue_branch(issue, project, author, branch)
     h = Gitlab::Application.routes.url_helpers
     link = h.namespace_project_compare_url(project.namespace, project, from: project.default_branch, to: branch)

spec/models/issue_spec.rb

@@ -131,7 +131,7 @@ describe Issue, models: true do
   end
 
   describe '#related_branches' do
-    it "should " do
+    it "selects the right branches" do
       allow(subject.project.repository).to receive(:branch_names).
                                     and_return(["mpempe", "#{subject.iid}mepmep", subject.to_branch_name])
 
@@ -151,10 +151,10 @@ describe Issue, models: true do
   end
 
   describe "#to_branch_name" do
-    let(:issue) { build(:issue, title: 'a' * 30) }
+    let(:issue) { create(:issue, title: 'a' * 30) }
 
     it "starts with the issue iid" do
-      expect(issue.to_branch_name).to match /\A#{issue.iid}-a+\z/
+      expect(issue.to_branch_name).to match /-#{issue.iid}\z/
     end
   end
 end