Bug: Ignore merge commits by default

[jerome-benoit]

I've already read the rationale in previous issues about why it will be not be done and found it rather fallacious: the goal of a commit message checking tool is to focus only on human inputs and bypass automated ones.

It's basically a human-machine inputs checker and not a machine-machine inputs checker. Furthermore, I do not see why adding a tunable to add a regex to ignore at various level would be an issue. For example, a simple GitHub or GitLab PR sync make to whole tool definitively fails in the PR branch without any possible workarounds and any strong rationale behind that.