Prettify indention in revisions view

[a.hoereth]

wp-admin/revision.php at the moment does not display indentations which are important when viewing code revisions. See attached images for examples.

Core most likely will bring back a maximum of one possible leading space per line. Having revisions.php display actual tabs or multiple spaces at line beginnings and multiple spaces in between words for better multi-line alignment would be nice.

To fix this revision.php requires table.diff { white-space: pre-wrap; } (will get into core according to ocean90) and ​wp_text_diff needs changes to not remove /[ \t]+/ in line 1708 and 1709. An alternative to ​normalize_whitespace might be required here. Changing the original function in core is not appropriate because it's expected to work the way it does.

[a.hoereth]

​.pre will be added to table.diff: ​#24425.

In addition removing normalize_whitespace from ​wp_text_diff (is pluggable) does the trick. This change will be restricted to posts of the code custom post type (post_id is passed on revision ajax requests) and should therefore not bring any unexpected changes to WP default behavior.

[a.hoereth]

CSS changes in [2047]

[a.hoereth]

In 2104:

Core has white-space: pre-wrap now. See #302

[a.hoereth]

In 2107:

Missed updating checksum on restore (see #303) and remove additional line padding in revision viewer (see #302)

[a.hoereth]

In 2109:

Redo correct part of [2107]:
Missed updating checksum on restore (see #303) and remove additional line padding in revision viewer (see #302)

[a.hoereth]

In 2115:

Only change padding when viewing revisions associated with posts of our custom post type. See #302

[a.hoereth]

In 2222:

Plugging wp_text_diff() function for preserving line breaks and multi-spacing in the revisions viewer when viewing code revisions. See #302