Cache the value of safe_message

Also, just for extra paranoia, only call safe_message once in the
decorator methods

Adds specs to make sure it still works

spec/models/commit_spec.rb

@@ -0,0 +1,37 @@
+require 'spec_helper'
+
+describe Commit do
+  let(:commit) { create(:project).commit }
+
+  describe CommitDecorator do
+    let(:decorator) { CommitDecorator.new(commit) }
+
+    describe '#title' do
+      it "returns no_commit_message when safe_message is blank" do
+        decorator.stub(:safe_message).and_return('')
+        decorator.title.should == "--no commit message"
+      end
+
+      it "truncates a message without a newline at 70 characters" do
+        message = commit.safe_message * 10
+
+        decorator.stub(:safe_message).and_return(message)
+        decorator.title.should == "#{message[0..69]}…"
+      end
+
+      it "truncates a message with a newline before 80 characters at the newline" do
+        message = commit.safe_message.split(" ").first
+
+        decorator.stub(:safe_message).and_return(message + "\n" + message)
+        decorator.title.should == message
+      end
+
+      it "truncates a message with a newline after 80 characters at 70 characters" do
+        message = (commit.safe_message * 10) + "\n"
+
+        decorator.stub(:safe_message).and_return(message)
+        decorator.title.should == "#{message[0..69]}…"
+      end
+    end
+  end
+end