Keep repository content at a specific version

By default, content from Git repositories stays updated with the repository's main branch, but you can configure the Puppetfile to maintain repository content at a specific version.

To specify a particular repository version you want to track, use one of the following options in the Git repository's declaration in your Puppetfile. Setting one of these options maintains the repository at the specified version and deploys any updates made to that particular version.

ref: Specifies the Git reference to check out. This option can reference either a tag, a commit, or a branch.

tag: Specifies a certain tag associated with the repo. For example:

mod 'apache',
  :git => 'https://github.com/puppetlabs/puppetlabs-apache',
  :tag => '0.9.0'

commit: Specifies a certain commit in the repo. For example:

mod 'apache',
  :git    => 'https://github.com/puppetlabs/puppetlabs-apache',
  :commit => '8df51aa'

branch: Specifies a certain branch of the Git repo or Declare content from a relative control repo branch. For example:
```
mod 'apache',
  :git    => 'https://github.com/puppetlabs/puppetlabs-apache',
  :branch => 'proxy_match'
```

In addition to one of the above options, you can also Set a default branch for content deployment.