I'm switching to using submodules for my vim plugins. The usual way of doing this is:
$ git submodule add https://github.com/vim-scripts/a.vim bundle/a.vim
Cloning into 'bundle/a.vim'...
etc, etc
This works fine with every plugin but Gundo:
$ git submodule add https://github.com/sjl/gundo.vim bundle/gundo
There is no output from running this command. The repo is added to .gitmodules and bundle/gundo is created, but is empty except for a .git file.
$ cd bundle/gundo
$ git status
# On branch (null)
#
# Initial commit
#
nothing to commit (create/copy files and use "git add" to track)
I'm completely new to submodules. What is special about this repository and how do I correctly add it?