General: Introduce wp_get_branch_version() helper to extract major.minor version safely.

[tejas0306]

This introduces a new helper function wp_get_branch_version() for extracting the WordPress branch version (major.minor) from a version string.

Currently, several different approaches are used across core to determine the branch version, including:

• (float) casting of get_bloginfo( 'version' )
• substr( $ver, 0, 3 )
• explode( '.' ) based parsing
• preg_split() in class-core-upgrader.php

Some of these approaches are fragile or incorrect:

• (float) casting can produce incorrect values due to floating-point precision issues.
• substr( $ver, 0, 3 ) breaks for versions >= 10.
• Multiple inconsistent approaches make maintenance harder.

This patch introduces wp_get_branch_version() using a string-based approach:

function wp_get_branch_version( $version = '' ) {
    if ( '' === $version ) {
        $version = wp_get_wp_version();
    }

    $parts = preg_split( '/[.-]/', $version, 3 );

    return $parts[0] . '.' . ( $parts[1] ?? '0' );
}

Trac ticket: https://core.trac.wordpress.org/ticket/64830

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[github-actions]

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[peterwilsoncc]

Suggested change

	}
	if ( 'minor' === $part ) {
	} elseif ( 'minor' === $part ) {

[peterwilsoncc]

I don't think this is required, the need in core isn't wide enough for what is relatively simple code.

[siliconforks]

The problem is that it's needed in about half a dozen different places in core. Currently these are using a mixture of different ad-hoc methods to find the version number, and some of these are actually wrong/buggy.

[tejas0306]

Thanks for the review.

The intention of wp_get_branch_version() here is mainly to consolidate several ad-hoc approaches currently used in core to derive the branch version.

At the moment, different files use different methods such as (float) casting, substr( $ver, 0, 3 ), or preg_split() / explode() logic. Some of these are fragile (for example substr( $ver, 0, 3 ) will break for versions >= 10, and (float) casting can produce incorrect results for x.0 branches).

This PR updates the current call sites that need the branch version to use a shared helper instead:

• wp-admin/admin-header.php
• wp-admin/includes/class-core-upgrader.php
• wp-admin/includes/class-wp-site-health-auto-updates.php
• wp-admin/includes/plugin-install.php
• wp-admin/includes/theme.php

The goal is mainly to keep the behavior consistent and avoid repeating slightly different parsing logic across these files.

Happy to adjust the implementation or limit the scope if a smaller change would be preferred.