adjacent_posts_rel_link ignores $excluded_categories argument

[adelval]

The ticket subject is pretty obvious, I think, just by looking at the source in link-template.php:

function adjacent_posts_rel_link($title = '%title', $in_same_cat = false, $excluded_categories = '') {
    echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', true);
    echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', false);
}

The $excluded_categories should be passed to get_adjacent_post_rel_link just as they come, not as an empty string.

Possible use cases of having the bug fixed:

• want to exclude a category from almost everywhere (because it has a single place in the blog), but it keeps appearing in the rel links.
• don't want to help robots discover posts from those categories through the rel links (robots.txt is not enforceable).

[SergeyBiryukov]

Introduced in [10815] along with the function itself.

next_post_rel_link() and prev_post_rel_link() are also affected.

[nacin]

Let's fix this. Oops!

[nacin]

In 27754:

Fix excluded_terms passed to get_adjacent_posts_rel_link().

props adelval.
fixes #22406.