Merge branch 'jk/complete-branch-force-delete'

The command line completion (in contrib/) completed "git branch -d" with branch names, but "git branch -D" offered tagnames in addition, which has been corrected. "git branch -M" had the same problem. * jk/complete-branch-force-delete: doc/git-branch: fix awkward wording for "-c" completion: handle other variants of "branch -m" completion: treat "branch -D" the same way as "branch -d"