The documentation[1] says that the ‘--numstat’ option for ‘git diff’ will
display ‘-’ for both added and deleted lines for binary files. This script uses
that to detect that binary files are being pushed and will reject them.
This is naive and simplistic. ‘git diff’ shows the same output when binary files
are deleted (or replaced with git-lfs placeholders), so this would prevent us
from fixing errors. But for now it helps us prevent accidental submissions of
binary files.
[1]: man 1 git-diff
