Revise [docs only] for repos that use circleCI for their docs build

[bsipocz]

Jobs shouldn't be run tests here:
https://travis-ci.org/astropy/astropy/builds/586132358?utm_source=github_status&utm_medium=notification

Also, now that many projects are moving their docs builds to circleCI from travis, [docs only] could be made a bit more clever, e.g. if there isn't even one docs job in the travis config the hole build should be cancelled without going into the individual jobs.

[pllim]

Yeah, something like not right with this logic somehow but my bash-fu is not strong enough...

ci-helpers/travis/setup_conda.sh

Lines 49 to 54 in e1bddf1

	elif [[ ! -z $(echo ${COMMIT_MESSAGE} | grep -E "${DOCS_ONLY}") ]]; then
	if ! [[ $SETUP_CMD =~ build_docs|build_sphinx|pycodestyle|flake8|pep8 ]] && [[ MAIN_CMD =~ pycodestyle|flake8|pep8 ]]; then
	# we also allow the style checkers to run here
	echo "Only docs build was requested by the commit message, exiting."
	travis_terminate 0
	fi

It looks as if [docs only] has no effect now; i.e., all the Travis jobs run regardless.

[pllim]

Maybe I broke it in #407 . 😭

[pllim]

I think this is now fixed?

[pllim]

Oh, wait... Haven't done "if there isn't even one docs job in the travis config the hole build should be cancelled without going into the individual jobs"... BUT do we really want that? I thought we still want PEP 8 job to run regardless.

[bsipocz]

There is a pep8 test on circleCI now, too, so it's all good to cancel the whole of travis.

[pllim]

But, only the core does that, not everyone else who uses ci-helpers?

[bsipocz]

oh, yes, you're right regarding that.

[pllim]

Maybe the title of the issue should at least be updated, as [docs only] is no longer broken.