Add commit message to JIRA's notification payload.

app/models/project_services/jira_service.rb

@@ -108,7 +108,8 @@ class JiraService < IssueTrackerService
       },
       entity: {
         name: noteable_name.humanize.downcase,
-        url: entity_url
+        url: entity_url,
+        title: noteable.title
       }
     }
 
@@ -196,10 +197,11 @@ class JiraService < IssueTrackerService
     user_url = data[:user][:url]
     entity_name = data[:entity][:name]
     entity_url = data[:entity][:url]
+    entity_title = data[:entity][:title]
     project_name = data[:project][:name]
 
     message = {
-      body: "[#{user_name}|#{user_url}] mentioned this issue in [a #{entity_name} of #{project_name}|#{entity_url}]."
+      body: %Q{[#{user_name}|#{user_url}] mentioned this issue in [a #{entity_name} of #{project_name}|#{entity_url}]:\n'#{entity_title}'}
     }
 
     unless existing_comment?(issue_name, message[:body])

spec/services/system_note_service_spec.rb

@@ -474,8 +474,8 @@ describe SystemNoteService, services: true do
 
       describe "existing reference" do
         before do
-          message = "[#{author.name}|http://localhost/u/#{author.username}] mentioned this issue in [a commit of #{project.path_with_namespace}|http://localhost/#{project.path_with_namespace}/commit/#{commit.id}]."
-          WebMock.stub_request(:get, jira_api_comment_url).to_return(body: "{\"comments\":[{\"body\":\"#{message}\"}]}")
+          message = %Q{[#{author.name}|http://localhost/u/#{author.username}] mentioned this issue in [a commit of #{project.path_with_namespace}|http://localhost/#{project.path_with_namespace}/commit/#{commit.id}]:\\n'#{commit.title}'}
+          WebMock.stub_request(:get, jira_api_comment_url).to_return(body: %Q({"comments":[{"body":"#{message}"}]}))
         end
 
         subject { described_class.cross_reference(jira_issue, commit, author) }