I have a workflow where I'm relying solely on the git history for version updates (no file changes).
You can turn off any file updates or other git changes by writing:

- id: bump
 name: Create bump
 uses: commitizen-tools/commitizen-action@master
 with:
 push: false
 commit: false

... and you get the expected output:

cz --no-raise 21 bump --yes --changelog --files-only
bump: version 0.0.0 → 0.1.0
tag to create: 0.1.0
increment detected: MINOR
Repository: someorg/somerepo
Actor: clockwork-muse
Not pushing
Done.

Unfortunately, this doesn't update outputs.version, leaving it at the previous version (0.0.0). This means I have to set commit: true, which disturbs the in-runner git state, which slightly complicates creation of releases (although in all honesty I probably should have done that anyways...).