Fix core_update_footer() for new Updates API

[afragen]

Fixes a regression in 5.6 with the changes in the new Updates API ​#meta5511.

The admin footer no longer displays the 'You are using a development version (%1$s). Cool! ... message when using the WP_AUTO_UPDATE_CORE constant set to update to beta or rc when the user is on a development version.

[SergeyBiryukov]

Thanks for the patch!

Since this is a regression and an easy fix, I think this is a good candidate for 5.6. Related: #51822.

[SergeyBiryukov]

Minor refresh to simplify the logic

[SergeyBiryukov]

In 49708:

Upgrade/Install: Display "You are using a development version" message in the admin footer for Beta or RC versions.

This ensures that the message is displayed when the WP_AUTO_UPDATE_CORE constant is set to beta or rc and the user is on a development version.

Props afragen.
Fixes #51892.

[SergeyBiryukov]

Reopening for backporting to the 5.6 branch after a second committer's review.

[azaozz]

[49708] looks good here, +1 to add to the 5.6 branch.

[SergeyBiryukov]

In 49711:

Upgrade/Install: Display "You are using a development version" message in the admin footer for Beta or RC versions.

This ensures that the message is displayed when the WP_AUTO_UPDATE_CORE constant is set to beta or rc and the user is on a development version.

Props afragen.
Reviewed by azaozz, SergeyBiryukov.
Merges [49708] to the 5.6 branch.
Fixes #51892.

[afragen]

test for $cur->version, replacing test for $cur->url

[hellofromTonya]

Removing for the re-opened issue.

[pbiron]

For the context behind 51892.3.diff​ see ​this slack thread.

[audrasjb]

Patch for alpha/beta/RC looks good to me.

For reference, it addresses the issue raised today ​in this thread in #core-auto-updates Slack channel.

[SergeyBiryukov]

To summarize the Slack thread linked above, if get_preferred_from_update_core() gets an empty response from get_core_updates(), it returns an object with 'response' => 'latest' and no other properties, so checking $cur->version without making sure it exists can cause a PHP warning.

Checking $wp_version instead would be more consistent with core_upgrade_preamble(), see [49709] / #51822.

Additionally, $cur->url is unused since [8595] and can be safely removed.

[SergeyBiryukov]

In 49736:

Upgrade/Install: Check $wp_version global for displaying "You are using a development version" message in the admin footer.

This brings some consistency with the same check in core_upgrade_preamble() and avoids a PHP warning if $cur->version is not set.

Additionally, remove the check for $cur->url property, unused since [8595].

Follow-up to [49708], [49709].

Props pbiron, afragen, audrasjb.
Fixes #51892.

[SergeyBiryukov]

Reopening for backporting to the 5.6 branch after a second committer's review.

[azaozz]

[49736] looks good here, +1 to merge to the 5.6 branch.

[SergeyBiryukov]

In 49743:

Upgrade/Install: Check $wp_version global for displaying "You are using a development version" message in the admin footer.

This brings some consistency with the same check in core_upgrade_preamble() and avoids a PHP warning if $cur->version is not set.

Additionally, remove the check for $cur->url property, unused since [8595].

Follow-up to [49708], [49709].

Props pbiron, afragen, audrasjb.
Reviewed by azaozz, SergeyBiryukov.
Merges [49736] to the 5.6 branch.
Fixes #51892.