If a file is read-only, it is marked with the closed lock icon in the Status bar, in its editor tab, or in the Project tool window. If a file is writable, then it is marked with the open lock icon in the Status bar. This section describes how to change read-only attribute of a file.
If a read-only status is set by a version control system, it's suggested that you use IntelliJ IDEA version control integration features. For more information, see Version Control with IntelliJ IDEA.