Use IO.popen instead of Kernel#` to read refs

spec/gitlab_projects_spec.rb

@@ -31,8 +31,8 @@ describe GitlabProjects do
     it "should create a branch" do
       gl_projects_create.exec
       gl_projects.exec
-      branch_ref = `cd #{tmp_repo_path} && git rev-parse test_branch`.strip
-      master_ref = `cd #{tmp_repo_path} && git rev-parse master`.strip
+      branch_ref = capture_in_tmp_repo(%W(git rev-parse test_branch))
+      master_ref = capture_in_tmp_repo(%W(git rev-parse master))
       branch_ref.should == master_ref
     end
   end
@@ -49,9 +49,9 @@ describe GitlabProjects do
     it "should remove a branch" do
       gl_projects_create.exec
       gl_projects_create_branch.exec
-      branch_ref = `cd #{tmp_repo_path} && git rev-parse test_branch`.strip
+      branch_ref = capture_in_tmp_repo(%W(git rev-parse test_branch))
       gl_projects.exec
-      branch_del = `cd #{tmp_repo_path} && git rev-parse test_branch`.strip
+      branch_del = capture_in_tmp_repo(%W(git rev-parse test_branch))
       branch_del.should_not == branch_ref
     end
   end
@@ -65,8 +65,8 @@ describe GitlabProjects do
     it "should create a tag" do
       gl_projects_create.exec
       gl_projects.exec
-      tag_ref = `cd #{tmp_repo_path} && git rev-parse test_tag`.strip
-      master_ref = `cd #{tmp_repo_path} && git rev-parse master`.strip
+      tag_ref = capture_in_tmp_repo(%W(git rev-parse test_tag))
+      master_ref = capture_in_tmp_repo(%W(git rev-parse master))
       tag_ref.should == master_ref
     end
   end
@@ -83,9 +83,9 @@ describe GitlabProjects do
     it "should remove a branch" do
       gl_projects_create.exec
       gl_projects_create_tag.exec
-      branch_ref = `cd #{tmp_repo_path} && git rev-parse test_tag`.strip
+      branch_ref = capture_in_tmp_repo(%W(git rev-parse test_tag))
       gl_projects.exec
-      branch_del = `cd #{tmp_repo_path} && git rev-parse test_tag`.strip
+      branch_del = capture_in_tmp_repo(%W(git rev-parse test_tag))
       branch_del.should_not == branch_ref
     end
   end
@@ -300,4 +300,8 @@ describe GitlabProjects do
   def repo_name
     'gitlab-ci.git'
   end
+
+  def capture_in_tmp_repo(cmd)
+    IO.popen(cmd, chdir: tmp_repo_path).read.strip
+  end
 end