mismatched output from interactive.diffFilter when adding the existence of new files

[llakala]

I've been testing the --patch mode for a couple of days with good results in almost all cases. The only problem I've found is when you do the following:

1. Create a new file with content

2. Use `git add --intent-to-add /path/to/file`

3. Now `git add -p` fails with the error below

fatal: mismatched output from interactive.diffFilter
hint: Your filter must maintain a one-to-one correspondence
hint: between its input and output lines.

Originally posted by @wvega-godaddy in #35 (comment)

Having the same issue here, on Git 2.47.0 and diff-so-fancy 1.4.4. I use --intent-to-add all the time in NixOS, because any untracked files are ignored by the system. Would love to see this fixed.