Fix various error messages and conditions in "git branch", e.g. we
advertised "branch -d/-D" to remove one or more branches but actually
implemented removal of zero or more branches---request to remove no
branches was not rejected.
* nd/branch-error-cases:
branch: let branch filters imply --list
docs: clarify git-branch --list behavior
branch: mark more strings for translation
branch: give a more helpful message on redundant arguments
branch: reject -D/-d without branch name