libostree: Enhance the annotation coverage

[tintou]

Increase the coverage of the GObject Introspection annotation and most notably replace the use of "allow-none" with "out" parameters to "nullable" or "optional" as the previous annotation is deprecated and ambiguous.

[openshift-ci]

Hi @tintou. Thanks for your PR.

I'm waiting for a ostreedev member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[cgwalters]

Thanks for the patch! Some overlap here with #2791 right?

[tintou]

This would probably help this PR indeed

[cgwalters]

OK before we do another semver bump I'd like to get a release out with current fixes for 0.17 #2818

[tintou]

I guess that this can be merged now?

[cgwalters]

/ok-to-test

[cgwalters]

/override continuous-integration/jenkins/pr-merge

[openshift-ci]

@cgwalters: Overrode contexts on behalf of cgwalters: continuous-integration/jenkins/pr-merge

In response to this:

/override continuous-integration/jenkins/pr-merge

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[cgwalters]

/override ci/prow/sanity

[openshift-ci]

@cgwalters: Overrode contexts on behalf of cgwalters: ci/prow/sanity

In response to this:

/override ci/prow/sanity

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[cgwalters]

Thanks!