Add a codeql-path output to the init action

[simon-engledew]

I've added a bare bones implemention of the codeql-path output variable. Opening this PR to get feedback and check it is aligned with expectations. 👍

• Expand readme documentation
• See if there is a better way of testing other than implicitly via the python-deps workflow (– added a second use of the output. Happy that the build will break if there is a regression.)

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Confirm the readme has been updated if necessary.

[chrisgavin]

👍 Awesome. It ended up being an even smaller change than I hoped and it seems like people will find it useful.

[simon-engledew]

I can't see an obvious way to test this feature other than the pair of integration tests I've added. The build will break if this feature stops working for any reason - is that good enough coverage?

I think we have consensus that this is enough testing for now 👍

I'm not super happy with the README changes. It feels like something is missing or the tone doesn't quite match the copy above. Happy to take suggestions for better wording. ✍️

Also I reference init@v1 which wont have this output. Should I reference init@main or make the current copy true by eventually backporting this change?

This can move into the documentation rather than the README

[chrisgavin]

Yep, I can see this is probably hard to test directly without it just being an assertion that codeQLCmd is correct, which is already tested in a bunch of other places.

Having the test in the workflow is pretty nice, even if it's not very explicit about what it's testing.

[simon-engledew]

I have left a comment of intent to hopefully make it more clear why this step is in the workflow 👍