Allow `get_comments_number()` to officially accept `$post` or `$post_id`. Adds unit tests.

Props coffee2code, JanHenkG.
Fixes #26240.

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git-svn-id: http://core.svn.wordpress.org/trunk@28384 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Read the `src` attribute for the `[embed]` shortcode if the shortcode's body is empty.

These work:
`[embed src="https://www.youtube.com/watch?v=ZqD-LPOWIT0"]`
`[embed src="https://www.youtube.com/watch?v=ZqD-LPOWIT0"][/embed]`

If you do:
`[embed src="https://www.youtube.com/watch?v=ZqD-LPOWIT0"]http://any-other-url.com[/embed]`

... "http://any-other-url.com" will be the URL that is parsed.

Props kovshenin, aaroncampbell for making initial patches.
Fixes #24456.


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git-svn-id: http://core.svn.wordpress.org/trunk@28385 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Truly check for `! empty()` instead of falsey `''` when determining whether to add `LIMIT` clause to SQL in `wp_get_archives()`.

Props jjeaton for the initial patch.
Fixes #27834.

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git-svn-id: http://core.svn.wordpress.org/trunk@28386 1a063a9b-81f0-0310-95a4-ce76da25c4cd
In `get_terms_to_edit()`, call `get_object_term_cache()` before priming cache with `wp_get_object_terms()`.

In `get_inline_data()`, do the same.

On list table screens with taxonomies in the admin, this dramatically reduces the number of database queries (3x less). Even more so with a persistent object cache (5x less).

Props johnbillion, jeffstieler, wonderboymusic.
Fixes #18968.


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git-svn-id: http://core.svn.wordpress.org/trunk@28387 1a063a9b-81f0-0310-95a4-ce76da25c4cd
When adding queries to `tax_query`: if the query's `field` is `term_taxonomy_id`, don't require `taxonomy` to be specified. In `WP_Tax_Query::transform_query()`, `$query['taxonomy']` is never checked for the 'term_taxonomy_id' `case` because 'term_taxonomy_id' is the primary key being looked up.

Adds unit tests.

Props helen.
Fixes #25284.


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git-svn-id: http://core.svn.wordpress.org/trunk@28388 1a063a9b-81f0-0310-95a4-ce76da25c4cd