How to invert `git log --grep=` or How to show git logs that don't match a pattern

I want to use git log to show all commits that do not match a given pattern. I know I can use the following to show all commits that do match a pattern:

git log --grep=<pattern>

How do I invert the sense of matching?

I am trying to ignore commits that have "bumped to version ..." in the message.

EDIT: I want my final output to be pretty verbose. e.g. git log --pretty --stat. So output from git log --format=oneline won't work for me.