下記のブログのエントリーのお陰でで解決。感謝です。
Gitでリモートブランチを消してもgit branch -aに出てくる件 - chulip.org
確かにgit fetchのmanには書いてあるんだけど、git branchのmanを見に行っちゃうし、多すぎてどこのman見に行けばいいのかわからない。
まあ俺は一生gitをマスターすることができないんだろうな・・・。
% git fetch --prune
x [deleted] (none) -> origin/add-random-featured
x [deleted] (none) -> origin/add_partial
x [deleted] (none) -> origin/award-badge
x [deleted] (none) -> origin/boards_anonymous_comment
x [deleted] (none) -> origin/change-story-end-menu-link-from-featured-to-top
x [deleted] (none) -> origin/convert-comic-frames
x [deleted] (none) -> origin/cookie-error
x [deleted] (none) -> origin/css-bug-in-read-comics
x [deleted] (none) -> origin/delete_comments
x [deleted] (none) -> origin/en-add-help-mokuji
x [deleted] (none) -> origin/enable-comment-from-cross-domain
x [deleted] (none) -> origin/exclude-authors-comments-from-recents
x [deleted] (none) -> origin/extract-simple_seed
x [deleted] (none) -> origin/feature-disable-anonymous-comments
x [deleted] (none) -> origin/fix-red-button-in-urban-legend
x [deleted] (none) -> origin/ignore-violation
x [deleted] (none) -> origin/iphone-icon-120
x [deleted] (none) -> origin/look-back-mode
x [deleted] (none) -> origin/modify-thank-you-mail
x [deleted] (none) -> origin/more_users_info
x [deleted] (none) -> origin/notice-tag-by-email
x [deleted] (none) -> origin/oulu-setup
x [deleted] (none) -> origin/poltergeist
x [deleted] (none) -> origin/rails4.1.1
x [deleted] (none) -> origin/random-story
x [deleted] (none) -> origin/remove_link
x [deleted] (none) -> origin/rmlink
x [deleted] (none) -> origin/scarystory
x [deleted] (none) -> origin/show-spoiler-checkbox-only-on-comic-and-story-pages
x [deleted] (none) -> origin/update-rails-from-3.2-to-4.0とにかくスッキリしました。