Creation of the main branch of an element
There is an exception to the rule that a branch can be created only at the master replica of the branch type. When you add a file to source control or create a new directory element, the main branch is created even if your current replica does not master the main branch type.
By default, the main branch of a new element is mastered by the replica that masters the main branch type, and you cannot create new versions on the branch. During element creation, you can specify an option to have your current replica master all newly created branches. For more information, see Assigning branch mastership during element creation.