a merge.abort command which deletes the branch and pops you back; (same as branch.delete <merge branch>)

[aryairani]

Even though we can currently use branch.delete as a workaround, it requires potentially a lot of typing which may or may not be easily tab-completable, depending on other existing branch names and merges in progress. A separate command would still be good.
(undo for such a command would also be good)