This is a feature request. After my team moved from Github to Phabricator, the big green merge button is the thing I miss the most.

In the page for a diff, there should be a big green button that says "Merge" which merges the diff into the target branch and closes the diff. This would be much more efficient and satisfying than the current method of opening a terminal, navigating to the right branch, and typing "arc land."

In Github, they automatically detect if a merge is possible and only show the button if it will succeed with no conflicts. I imagine the way this is implemented is using something like this git command: http://stackoverflow.com/questions/501407/is-there-a-git-merge-dry-run-option.