What is a merge commit?

A merge commit is specifically a commit that serves as a record of a merge operation. When two branches in a version control system, such as Git, are merged together, a merge commit is created to record the integration of changes from both branches. This commit contains two parent commits, reflecting the histories of both branches being merged, which allows the version control system to maintain a clear and historical view of how the project evolved.

This functionality is crucial because it preserves the context of the changes that were made on both branches before they were combined. As a result, if developers need to look back at history or troubleshoot issues, they can trace through these merge commits to understand how and why changes were made.

In contrast, other choices describe different types of commits or actions that do not accurately represent the purpose of a merge commit. For example, adding new files or deleting previous versions of files pertains to different commit actions rather than the specific concept of merging. Additionally, the idea of a commit being unable to be changed or undone does not apply to merge commits uniquely, as all commits in a version control system can be modified or reverted under certain conditions, making it not a defining characteristic of a merge commit.