Conflict with FastFold plugin slows down window switching a lot.

[rcaputo]

I've been looking into a slowdown in the FastFold plugin when switching to a ledger window. It turns out that it may be dueling autocmd handlers. The discussion is at Konfekt/FastFold#48 and it begins to get interesting for vim-ledger at Konfekt/FastFold#48 (comment)

The very short version is that ftdetect/ledger.vim should avoid setting the filetype on BufEnter, only on BufRead.

This is working very well for me:

% cat ftdetect/ledger.vim
autocmd BufRead *.ldg,*.ledger setlocal filetype=ledger | compiler ledger

The medium version is that windo will trigger BufEnter on a ledger. If that windo is invoked as part of autocmd FileType, it will complete a loop with vim-ledger:

• Ledger autocmd BufEnter does setlocal filetype.
• FastFold autocmd FileType triggers Ledger's BufEnter.
• This locks up vim for several seconds depending on the size of the ledger file.

To be fair, FastFold uses noautocmd windo. For some reason I haven't determined it's still triggering autocmds.

You can see the looping happen in the verbose.log, which I've excerpted at Konfekt/FastFold#48 (comment)

[kljohann]

Thanks for tracking this down! After looking at filetype.vim shipped with vim I think we should switch to au BufNewFile,BufRead setf ledger. For setting the compiler option we should include the following in ftplugin/ledger.vim:

if !exists('current_compiler')
  compiler ledger
endif