Fix default branch reference in GitHub Actions workflow definitions

[japborst]

In #253 the GHA workflow was edited to use $default-branch. Whilst this works in workflow templates, this actually doesn't in a workflow.

Here, we revert to referencing master directly.

[Stephan202]

Nice catch! For others: see also this.

Suggested commit message:

Fix default branch reference in GitHub Actions workflow definitions (#278)

[Stephan202]

We could still do:

Suggested change

	branches:
	- master
	branches: [ master ]

(Assuming the earlier intention was to match jdk: [ 11.0.16, 17.0.4 ] below. Or we could change both to multi-line lists. Maybe that's nicer?)

[rickie]

IMO the jdk field is a bit different as for matrix that is the way to define the values, see here.

AFAICS that is the only way there. For branches, especially if it is only one, I prefer the - master way.

WDYT?

[japborst]

The docs also use both approaches, not very consistent. [something] is the same as - something, so in the end shouldn't matter. It can be a shorthand, which are especially helpful for matrices, whereas branches are longer to begin with.

jdk: [ 11.0.16, 17.0.4 ]

instead of

jdk:
 - 11.0.16
 - 17.0.4

Nevertheless, I don't see us expanding this list to a wide range, so using the shorthand is pretty clean.

[rickie]

One answer/question.

Already approving as it is not a blocker.

[rickie]

IMO the jdk field is a bit different as for matrix that is the way to define the values, see here.

AFAICS that is the only way there. For branches, especially if it is only one, I prefer the - master way.

WDYT?

[rickie]

Okay clear, let's merge when the build is green 😄.