/usr/share/vim/addons/ftdetect/haproxy.vim is in vim-haproxy 1.4.24-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | " detect HAProxy configuration
au BufRead,BufNewFile haproxy*.cfg set filetype=haproxy
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