Folder comparisons support the automatic merging of folders into a common ancestor folder, in a similar manner to file comparisons. The first and third folders will typically be independently modified copies of the common ancestor (middle) 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.
Performing an automatic merge
The automatic merging operation will merge changes from the first and third folders back into the common ancestor folder. The operation can involve removal, copying, and automatic merging of files.
To perform an automatic folder merge:
- Perform a folder comparison between three folders. Merge will assume that central folder is the common ancestor of the first and third folders.
- Make a backup copy of the common ancestor folder. Merge cannot undo changes that it makes to the contents of the common ancestor folder.
- Select the rows in the folder comparison results list that you want to include in the automatic merging operation. You can select all files in the list by pressing Ctrl+A. Note that the automatic merge operation will ignore any selected folders.
- Click the Merge to common ancestor
button in the ribbon to review what will be done by the merging operation. - Review the proposed actions in the Merge to Common Ancestor window. Click Start to begin the operation.
- Merge will perform the merging operation, reporting any errors or warnings as they are encountered.
Understanding automatic merge results
When an automatic merge completes, the folder comparison window is updated to show what happened.
If you have enabled the option to Keep unchanged rows hidden in the ribbon Hide/reveal 
menu, rows that are now unchanged as a result of the merging operation will disappear from view.
Rows that were successfully merged will show a resolved marker 
, and the relevant filenames will be dimmed.
Edit markers indicate the nature of each change:
- For files copied into the common ancestor, the row is marked with an arrow (
or 
) indicating the folder hierarchy (right or left) from which the files were copied. - For files removed from the common ancestor, a delete marker
is placed on the row after the position from which the files were removed. - For files that have been automatically merged to the common ancestor, the row is marked with
.
To navigate between edit markers:
- click the Previous edit
and Next edit 
ribbon buttons; - or, press Ctrl+7 and Ctrl+8.
A conflict marker 
is attached to files that either could not be merged due to merging conflicts or unexpected errors. In either case, the marker’s comment will describe the problem.
To navigate between conflicts:
- click the Previous conflict
and Next conflict 
toolbar buttons; - or, press Ctrl+9 and Ctrl+0 (zero).
Each , , , or marker has an associated tooltip that explains what change was made. Conflict markers also have a tooltip to explain the reason for the conflict. Hold the mouse cursor over the marker for a few seconds to see the explanation. Alternatively, right-click on the edit marker and select Edit Comment… from the context menu.
Files that could not be merged automatically due to merging conflicts should be merged manually using a file comparison.
How automatic merging works
The following rules define what will happen to selected files during an automatic merging operation:
| First Folder | Second Folder | Third Folder | Action |
|---|---|---|---|
| File | Copy the file to the second folder. | ||
| File | Delete the file. | ||
| File | File | If the files are unchanged then remove the file in the second folder, otherwise mark it as a conflict. | |
| File | Copy the file from the first folder to the second folder. | ||
| File | File | Merge the files in the first and third folders into the second folder.† | |
| File | File | If the files are unchanged then remove the file in the second folder, otherwise mark it as a conflict. | |
| File | File | File | Merge the files in the first and third folders into the second folder.† |
† Files are only merged if they are considered to be text files.