How it works...

In the preceding example, <vcs> is the version control system being used; it could be a local server or an online service such as, GitHub. <tag_name> is the version control tag used to identify this particular update to the control system.

If a required dependency was a top-level requirement for the project, then that particular line in the requirements file can simply be replaced. If it is a sub-dependency of another file, then the above command would be added as a new line.