Docs: Link to the "Conditional Tags" article in the Theme Developer Handbook from the descriptions for a variety of core conditional tag functions.

These notations largely serve to direct consumers (of both the source and the parsed code reference) to extended information on individual and related conditional tags throughout WordPress. The changeset also standardizes corresponding DocBlock summaries to use third-person singular verbs.

Notations been added for the following functions:

* comments_open()
* email exists()
* has_excerpt()
* has_post_thumbnail()
* has_tag()
* in_category()
* in_the_loop()
* is_404()
* is_active_sidebar()
* is_active_widget()
* is_admin()
* is_admin_bar_showing()
* is_archive()
* is_attachment()
* is_author()
* is_blog_installed()
* is_category()
* is_comments_popup()
* is_date()
* is_day()
* is_dynamic_sidebar()
* is_feed()
* is_front_page()
* is_home()
* is_local_attachment()
* is_main_query
* is_month()
* is_multi_author
* is_new_day()
* is_page()
* is_page_template()
* is_paged()
* is_plugin_active()
* is_plugin_active_for_network()
* is_plugin_inactive()
* is_plugin_page()
* is_post_type_archive()
* is_preview()
* is_rtl()
* is_search()
* is_single()
* is_singular()
* is_sticky()
* is_tag()
* is_tax()
* is_taxonomy_hierarchical()
* is_time()
* is_trackback()
* is_user_logged_in()
* is_year()
* pings_open()
* post_type_exists()
* taxonomy_exists()
* term_exists()
* username exists()
* wp_attachment_is_image()
* wp_script_is()

Props janalwin.
Fixes #43254.


git-svn-id: https://develop.svn.wordpress.org/trunk@42710 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/post.php

@@ -971,7 +971,11 @@ function is_post_type_hierarchical( $post_type ) {
 }
 
 /**
- * Check if a post type is registered.
+ * Determines whether a post type is registered.
+ * 
+ * For more information on this and similar theme functions, check out
+ * the {@link https://developer.wordpress.org/themes/basics/conditional-tags/ 
+ * Conditional Tags} article in the Theme Developer Handbook.
  *
  * @since 3.0.0
  *
@@ -1981,11 +1985,15 @@ function get_post_custom_values( $key = '', $post_id = 0 ) {
 }
 
 /**
- * Check if post is sticky.
+ * Determines whether a post is sticky.
  *
  * Sticky posts should remain at the top of The Loop. If the post ID is not
  * given, then The Loop ID for the current post will be used.
- *
+ * 
+ * For more information on this and similar theme functions, check out
+ * the {@link https://developer.wordpress.org/themes/basics/conditional-tags/ 
+ * Conditional Tags} article in the Theme Developer Handbook.
+ * 
  * @since 2.7.0
  *
  * @param int $post_id Optional. Post ID. Default is ID of the global $post.
@@ -5045,8 +5053,12 @@ function get_pages( $args = array() ) {
 //
 
 /**
- * Check if the attachment URI is local one and is really an attachment.
- *
+ * Determines whether an attachment URI is local and really an attachment.
+ * 
+ * For more information on this and similar theme functions, check out
+ * the {@link https://developer.wordpress.org/themes/basics/conditional-tags/ 
+ * Conditional Tags} article in the Theme Developer Handbook.
+ * 
  * @since 2.0.0
  *
  * @param string $url URL to check
@@ -5520,7 +5532,11 @@ function wp_attachment_is( $type, $post = null ) {
 }
 
 /**
- * Checks if the attachment is an image.
+ * Determines whether an attachment is an image.
+ * 
+ * For more information on this and similar theme functions, check out
+ * the {@link https://developer.wordpress.org/themes/basics/conditional-tags/ 
+ * Conditional Tags} article in the Theme Developer Handbook.
  *
  * @since 2.1.0
  * @since 4.2.0 Modified into wrapper for wp_attachment_is() and