Choose gzdev branch on PR / manual jobs

[chapulina]

It would be useful to be able to choose a gzdev branch on PR / manual jobs like this one:

https://build.osrfoundation.org/job/ignition_gazebo-ci-pr_any-ubuntu_auto-amd64/build?delay=0sec

This came up while testing a pre-release for this PR: gazebosim/gz-sim#661 (comment)

[scpeters]

it would be convenient if we could add a label to a pull request in order to build with prerelease or nightly packages

[chapulina]

You dream big! ✨

[scpeters]

I have an alternative proposal in #564

[chapulina]

I have an alternative proposal in #564

I think that works for PRs bumping versions, but that wouldn't cover the use case of PRs testing pre-releases. For example, to test gazebosim/gz-sim#869 against an ign-physics pre-release, we had to open a PR against gzdev like this: gazebo-tooling/gzdev#37 and then revert with another PR like this: gazebo-tooling/gzdev#39

[scpeters]

For example, to test gazebosim/gz-sim#869 against an ign-physics pre-release, we had to open a PR against gzdev like this: gazebo-tooling/gzdev#37 and then revert with another PR like this: gazebo-tooling/gzdev#39

I think we could create a gzdev branch with matching name that uses prereleases, and it would use that for CI. We wouldn't even have to create a gzdev pull request. It does get more tricky to know which branches should be merged because CI could pass in a PR and then fail after merging if you don't merge the infrastructure branches properly. Overall, though, I think it would work for this case too.