Support Adding and Removing of branches and tags

This commit adds support to create and remove branches and tags from gitlab-shell.

The code style was followed as closely as possible to the original.

The purpose of this commit is that I will be adding support to the Gitlabhq (Gitlab) project
in order to allow adding and removing of branches and tags through their API.

lib/gitlab_projects.rb

@@ -25,6 +25,10 @@ class GitlabProjects
 
   def exec
     case @command
+    when 'create-branch'; create_branch
+    when 'rm-branch'; rm_branch
+    when 'create-tag'; create_tag
+    when 'rm-tag'; rm_tag
     when 'add-project'; add_project
     when 'rm-project';  rm_project
     when 'mv-project';  mv_project
@@ -38,6 +42,32 @@ class GitlabProjects
 
   protected
 
+  def create_branch
+    branch_name = ARGV.shift
+    ref = ARGV.shift || "HEAD"
+    cmd = "cd #{full_path} && git branch #{branch_name} #{ref}"
+    system(cmd)
+  end
+
+  def rm_branch
+    branch_name = ARGV.shift
+    cmd = "cd #{full_path} && git branch -D #{branch_name}"
+    system(cmd)
+  end
+
+  def create_tag
+    tag_name = ARGV.shift
+    ref = ARGV.shift || "HEAD"
+    cmd = "cd #{full_path} && git tag #{tag_name} #{ref}"
+    system(cmd)
+  end
+
+  def rm_tag
+    tag_name = ARGV.shift
+    cmd = "cd #{full_path} && git tag -d #{tag_name}"
+    system(cmd)
+  end
+
   def add_project
     FileUtils.mkdir_p(full_path, mode: 0770)
     cmd = "cd #{full_path} && git init --bare && #{create_hooks_cmd}"