bash completion: Use 'git add' completions for 'git stage'

Signed-off-by: Lee Marlow <lee.marlow@gmail.com>
Trivially-Acked-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -1738,6 +1738,7 @@ _git ()
 	show)        _git_show ;;
 	show-branch) _git_show_branch ;;
 	stash)       _git_stash ;;
+	stage)       _git_add ;;
 	submodule)   _git_submodule ;;
 	svn)         _git_svn ;;
 	tag)         _git_tag ;;