Add tests for Committer#==

spec/lib/gitlab/git/committer_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Git::Committer do
+  let(:name) { 'Jane Doe' }
+  let(:email) { 'janedoe@example.com' }
+  let(:gl_id) { 'user-123' }
+
+  subject { described_class.new(name, email, gl_id) }
+
+  describe '#==' do
+    def eq_other(name, email, gl_id)
+      eq(described_class.new(name, email, gl_id))
+    end
+
+    it { expect(subject).to eq_other(name, email, gl_id) }
+
+    it { expect(subject).not_to eq_other(nil, nil, nil) }
+    it { expect(subject).not_to eq_other(name + 'x', email, gl_id) }
+    it { expect(subject).not_to eq_other(name, email + 'x', gl_id) }
+    it { expect(subject).not_to eq_other(name, email, gl_id + 'x') }
+  end
+end