Disallow tabs in Travis CI

[fitzgen]

This addresses some concerns raised in #142, but perhaps it also makes sense to expand this beyond creduce.in to the rest of the code base.

[eeide]

I don't really want to fail the Travis-CI build due to violated style rules.

In #142 I said that it was the best I knew how to do—but that doesn't mean that I really want to do it.

There must be a better approach to enforcing style rules. Isn't there? We should find it.

[fitzgen]

FWIW, it should still run the make check, but will report the overall run as a failure if there are tabs. I am unsure what your specific concern with running style checks in Travis CI is. The desire to allow style issues to be dealt with later?

[fitzgen]

Is it because

The closest thing that I know how to do would be to fail the Travis-CI build—which would enforce a kind of "punishment," but doesn't prevent the push from happening.

You can set up the master to disallow direct pushes, and require everything to go through a PR for which CI passes.

Depends on whether you think it the added ceremony pays for itself or not.

[regehr]

I agree that it would be good to make "make check" fail but not to make the CI fail on this issue.

[eeide]

Ideally, I would like style issues to be dealt with before the CI build. It seems silly to me for style rules to be enforced so late in the pipeline.

At the same time, I'm not sure how to enforce them both (1) for everybody and (2) earlier. This is worth some investigation, I think, before committing to something (ha ha).

(Surely other GitHub-hosted projects enforce style rules automatically; how do they do it? Do they all do it as you outline, by requiring commits to master to come from pull requests that have been vetted by the CI?)

[regehr]

I imagine so. I find pull reqs heavyweight for such a small project as this, but could be convinced otherwise.