This looks ok to me -- do we want to also notify users that it has skipped an update due to incompatible PHP requirements? I'm ok if that is another PR too. Should we confirm adding something to the release process first?

This looks ok to me -- do we want to also notify users that it has skipped an update due to incompatible PHP requirements? I'm ok if that is another PR too.

You mean similar to wp-cli/extension-command#440 where we say that a specific version is unavailable/incompatible?

Should we confirm adding something to the release process first?

Good point. This will indeed require a slight addition to the release process, as this JSON file will need to be uploaded to every GitHub release going forward. Unless we find a better way to do this of course.

I hope @schlessera can share his thoughts soon on that.

You mean similar to wp-cli/extension-command#440 where we say that a specific version is unavailable/incompatible?

Yea something similar to that. Really just a message that lets you know that wp cli update is holding something back. Otherwise you might think that by showing no update available you are on using the latest version (which was part of the problem with themes and plugins -- not knowing that new versions are available and thinking you are up to date when it says no updates available).

Overall it is much less of an issue with a tool like wp-cli because there is just one thing to keep track of and most people are probably following it upstream as well, so I don't think its the same level of problem as with themes/plugins and more of a nice to have at some point.

Good suggestion 👍 If not for wp cli update this would be something for wp cli check-update.

In the future this could also be used for other things like versions that are not offered because of known security issues or so, so maybe we can incorporate that logic already.

I just pushed changes to a) check the PHP version required by a nightly build as well and b) update the table's output as per @mrsdizzie's suggestion. Example:

 $ wp cli check-update
+-----------+-------------+-------------------------------------------------------------------------------------+-------------+---------------+
| version   | update_type | package_url                                                                         | status      | requires_php  |
+-----------+-------------+-------------------------------------------------------------------------------------+-------------+---------------+
| 999.9.9   | major       | https://github.com/wp-cli/wp-cli/releases/download/v999.9.9/wp-cli-999.9.9.phar     | unavailable | 123.4.5       |
| 777.7.7   | major       | https://github.com/wp-cli/wp-cli/releases/download/v777.7.7/wp-cli-777.7.7.phar     | available   | 5.6.0         |
+-----------+-------------+-------------------------------------------------------------------------------------+-------------+---------------+