Which function is used to merge a complete branch into the mainline and is only available on the main line?

The function that is utilized to merge a complete branch into the mainline and is accessible solely on the main line is the merge feature branch function. This operation is specifically designed for integrating the changes from a feature branch back into the primary working branch (often referred to as the main line or master).

When you have developed a new feature or made significant changes in a separate branch, you eventually want to combine those changes into the main codebase. The merge feature branch function allows you to do this seamlessly, ensuring that all the commits associated with that feature branch are integrated properly into the mainline.

This process may include conflict resolution if there are overlapping changes between the mainline and the feature branch. It's important to note that this function is distinct from other operations that may occur in different contexts or branches, emphasizing that it should only be executed from the main line. This ensures that the main branch remains stable while integrating new features effectively.

In contrast, other options like branch merge, rebase, and fast-forward merge represent different concepts or scenarios in version control management. While they have their own specific uses, they do not encapsulate the action of merging a complete feature branch specifically from the main line, which makes the merge feature branch function the correct choice