Scan all unmerged Vim commits to determine which commits are N/A
for Neovim.
vim_na_regexp.txt contains the file patterns to filter out N/A files
in a Vim commit.
vim_na_files.txt contains "absolute filepath" of N/A files.
It relies on vim_na_regexp.txt to reduce file size.
If version.c remains and it has the expected 2-liner update,
then it's considered N/A.
https://github.com/neovim/neovim/discussions/36326
