Can't remove dependency without breaking git

We want to remove the `pre-git` dependency from one of our repos that's used semi-regularly across two big teams. The problem we've found is that the pre-commit hooks have already been installed in the repo checkouts of anyone that has built it before. Thus, if we remove the dependency all of their git actions will fail because `./node_modules/.bin/commit-msg` is missing.

This would be really simple to fix by wrapping `./node_modules/.bin/commit-msg` in a if clause, and make removing this dependency much easier.

Inspect the pre-commit hook setup that invokes ./node_modules/.bin/commit-msg and trace how the pre-git dependency installs it. Verify the hook safely handles that executable being absent, then test git actions in a checkout where the dependency is no longer installed.

Written by the indexing model from the issue text.