The easiest way for users to define their own maps in Gstatus buffers is
using a ftplugin/fugitive.vim file with a `b:fugitive_type != 'index'`
guard. Setting the filetype after defining the maps allows users to
maniuplate "dangerous" maps and otherwise customize mappings.
For example, in ~/.vim/after/ftplugin/fugitive.vim:
if !exists('g:loaded_fugitive') || b:fugitive_type != 'index'
finish
endif
" Use s to stage *and* unstage changes: shadows -.
nmap <buffer> <silent> s -
xmap <buffer> <silent> s -
" I hit this by accident.
nunmap <buffer> X
