You can select all files in the list by pressing Ctrl + A. Merge cannot undo changes that it makes to the contents of the common ancestor folder. Merge will assume that central folder is the common ancestor of the first and third folders. The operation can involve removal, copying, and automatic merging of files.

The automatic merging operation will merge changes from the first and third folders back into the common ancestor folder. Please see Three-Way File Comparison and Merging for information about the general circumstance that may result in three distinct revisions of a set of files needing to be combined. The first and third folders will typically be independently modified copies of the common ancestor (middle) folder.

Folder comparisons support the automatic merging of folders into a common ancestor folder, in a similar manner to file comparisons.