How can user permissions be assigned in a GitLab project?

User permissions in a GitLab project are managed primarily through the process of adding users to the project and assigning them specific roles. This role assignment allows for various levels of access and permissions, which include Guest, Reporter, Developer, Maintainer, and Owner. Each role comes with a distinct set of permissions that dictate what actions a user can perform within the project, such as pushing code, managing settings, or merging merge requests.

The ability to finely tune who can do what within a project is crucial for maintaining security and collaboration efficiency. By assigning the appropriate role to each user, project maintainers can control the workflow and ensure that individuals can only perform actions that are pertinent to their responsibilities within the project.

The other methods mentioned do not relate to assigning user permissions directly. Creating a new issue is focused on project management, forking a project repository is about duplicating a project, and setting environment variables pertains to configuration settings rather than user access control. Therefore, the correct approach to managing user permissions in GitLab is by adding users to the project and assigning them specific roles.