git merge with removed secrets in diff causes commit to fail

[Kyle-sandeman-mrdfood]

Steps to reproduce:

1. create git repo
2. commit some secrets on branch X
3. create branch Y which removes those secrets
4. merge Y into X: git checkout X && git merge Y --no-ff (a fast forward would happen for this simple case, let's skip that)

if it matters, alias gm='git merge'

Mac OSX Catalina, using git 2.25.0 creates a diff after the comments for a git merge:

The diff after the separator is NOT included in the actual commit message, but presumably because it is fed through STDIN, git-secrets refuses to commit. Additionally, git merge --no-verify does not seem to work (git commit --no-verify does work)