vim: add command to retrieve branch description

This helps if the description stores common trailers (though a hook
might be better than having to remember).

Author: benknoble

links/vim/after/ftplugin/gitcommit.vim

@@ -16,6 +16,7 @@ setlocal comments+=b:>
 nnoremap <buffer> <LocalLeader>d :DiffGitCached<CR>
 
 command -buffer -bar -nargs=? Ref execute 'read !git show --no-patch --format=reference' empty(<q-args>) ? @* : <q-args> | -join
+command -buffer -bar Describe read !git config branch.$(git branch --show-current).description
 
 let b:undo_ftplugin = bk#ftplugin#undo(#{
       \ opts: [
@@ -31,5 +32,6 @@ let b:undo_ftplugin = bk#ftplugin#undo(#{
       \ ],
       \ commands: [
       \   'Ref',
+      \   'Describe',
       \ ],
       \ })