[wp-trac] [WordPress Trac] #6775: Post Revisions

[WordPress Trac]

#6775: Post Revisions
-------------------------+--------------------------------------------------
 Reporter:  mdawaffe     |       Owner:  anonymous             
     Type:  enhancement  |      Status:  new                   
 Priority:  normal       |   Milestone:  2.6                   
Component:  General      |     Version:  2.5.1                 
 Severity:  normal       |    Keywords:  revision needs-testing
-------------------------+--------------------------------------------------
 == Overview ==

 Attached is a first pass at adding basic versioning/revisioning to
 WordPress.

 What it does:
  1. Saves a copy of a post every time you edit it.
  2. Allows you to view (not edit) each of those copies (revisions).
  3. Shows diffs between any two revisions.  Forward (in time) diffs only.

 What it doesn't do:
  1. You cannot have a live-revision and a working revision to be pushed
 live later.  I'm not sure if that feature would be useful to our core
 audience or not.  At any rate, it's a little tricky to get working
 correctly.

 == How it works ==

 Posts are copied into a new row in the posts table on the
 {{{pre_post_update}}} hook.  Only certain (configurable by plugin) fields
 are saved (title, content, author, excerpt).  The rest are either used
 internally by WP somewhere or I felt weren't useful to save.

 Posts can be restored from an older revision either in full or field by
 field (not chunk by chunk).

 The Diff engine is an extension of the
 [http://pear.php.net/package/Text_Diff PEAR Text_Diff] package (which I
 believe to be the descendent of the MediaWiki Diff engine).  The
 generation of the diff output is fully pluggable via the new
 {{{wp_text_diff()}}} pluggable function.

 The provided function shows diffs "side by side" and with both line and
 word highlighting (trac style).  The old content is on the left, and the
 new content is on the right.  This presentation allows you to ignore all
 the color highlighting and plusses and minuses and just read either side
 from top to bottom to see what the post looked like in that revision.

 Functions provided:
  * {{{wp_text_diff( $left_string, $right_string, $args = null )}}}
  * {{{wp_save_revision( $post_id )}}}
  * {{{wp_get_revision(&$post, $output = OBJECT, $filter = 'raw')}}}
  * {{{wp_restore_revision( $revision_id, $fields = null )}}}
  * {{{wp_delete_revision( $revision_id )}}}
  * {{{wp_get_post_revisions( $post_id = 0 )}}}
  * {{{wp_list_post_revisions( $post_id = 0, $args = null )}}}

 == TODO ==

  1. Open up revisions for pages as well.  That's where they'll be most
 useful.
  2. Rework Autosave to store its data as a special post revision.  Then
 we'll be able to autosave *all* posts/pages (not just drafts) and have
 recovery messages like "WordPress found an autosaved copy of this post
 that's more recent than your version, would you like to see it?"
  3. Review caps/permissions.  Do we need any new ones like
 {{{current_user_can( 'view_revision', $id )}}}?
  4. Display revisions and/or diffs in front end?
  5. Decide how many revisions to store for each post.  Right now it stores
 an arbitrary number.  Should it be capped?

 == Prior work and idea sources ==
  1. http://wordpress.org/extend/plugins/post-revisions/ (me)
  2. http://wordpress.org/extend/plugins/blicki/ (Ryan)
  3. http://comox.textdrive.com/pipermail/wp-hackers/2008-March/018689.html
 (Paul Menard)

 Committer:
 {{{
 svn add wp-includes/Text
 svn add wp-incledes/wp-diff.php
 svn add wp-admin/revision.php
 }}}

-- 
Ticket URL: <http://trac.wordpress.org/ticket/6775>
WordPress Trac <http://trac.wordpress.org/>
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