	Remove a TopGit-controlled topic branch of the given name
	(required argument). Normally, this command will remove only an
	empty branch (base == head) without dependendents; use '-f' to
	remove a non-empty branch or a branch that is depended upon by
	another branch.

	The '-f' option is also useful to force removal of a branch's
	base, if you used `git branch -D B` to remove branch B, and then
	certain TopGit commands complain, because the base of branch B
	is still there.

	IMPORTANT: Currently, this command will _NOT_ remove the branch
	from the dependency list in other branches. You need to take
	care of this _manually_.  This is even more complicated in
	combination with '-f' - in that case, you need to manually
	unmerge the removed branch's changes from the branches depending
	on it.

	TODO: '-a' to delete all empty branches, depfix, revert

