The Merge - Abort option is available when a branch merge results in merge conflicts.
To use this action, navigate to the Git repository folder in the Version Control tab. Right-click the folder and select Version Control -> Merge - Abort. When the confirmation dialog is displayed, press OK. This will run the "git merge –abort" command which aborts the merge process and tries to reconstruct the pre-merge state. See Git documentation for further details.
You are notified if a merge is pending awaiting conflicts to be resolved. A status notification bar appears at the top of the Version Control view. The Git Status column also shows Merge Pending for the Git repository folder and Conflict for the files that are in conflict.