Revisions: Re-think the way how the current revision is detected

[ocean90]

To detect if a revision is the current one we do $revision->post_modified_gmt === $post->post_modified_gmt, see trunk/wp-admin/includes/revision.php:24708#L102​.

This can be an issue if you are using the API and creating revisions programmatically which can result in same timestamps, since we doesn't save milliseconds, only seconds.

We noticed this while the GSoC project "Code revisions", see ​#gsoc326 and on ​make/core.

Not sure if we can do something here, but want to make it known.

[ocean90]

fixes typo

[ocean90]

24782.2.diff​ works for me. Tested with Code Revisions and some test posts. Works also with an autosave as latest revision.

[nacin]

Works also with an autosave as latest revision.

24782.3.diff​ tries to make absolutely sure that an autosave will not accidentally be considered to be the current revision. Some odd set of closely timed events, I guess, could cause this.

[markjaquith]

I'm good with this.

[nacin]

In 24730:

If two revisions were created at the same time, mark the one with the greater ID as current. Also avoid flagging autosaves as current. fixes #24782.

[nacin]

Note:

	// If a post has been saved since the last revision (no revisioned fields were changed)
	// we may not have a "current" revision. Mark the latest revision as "current".
	if ( empty( $current_id ) )
		$revisions[ $revision->ID ]['current'] = true;

... being added in #24804 (first appearance is .9.diff).