Introduce pre_move_uploaded_file filter to allow pre-processing of uploaded files

[ryan]

This is handy for use in file replication plugins. We've been using this on wordpress.com for awhile for just that purpose.

[Mte90]

refreshed patch

[Mte90]

working refreshed patch

[Mte90]

Ignore the 24603.patch this is a wrong testing patch, the real refreshed patch is 24603.2.patch.

[johnbillion]

@Mte90 Can you add a docblock for the new filter please?

[Mte90]

added docs

[Mte90]

Replying to johnbillion:

@Mte90 Can you add a docblock for the new filter please?

Done, I don't know if I written in the best way.

[DrewAPicture]

@Mte90 Updated patch looks pretty good. There's just a couple things I wanted to note that I'll go ahead and fix on commit:

• There should be a space between the DocBlock summary and description
• In the case of "real" values like null we typically assign "pseudo-variables" in the DocBlock so as to best illustrate what the value to represents. In this case, we'll probably just reuse $move_new_file

[DrewAPicture]

In 41258:

Filesystem: Introduce the pre_move_uploaded_file filter.

Passing a non-null value to the filter will prevent the uploaded file from being moved to the uploads directory for any of the functions leveraging _wp_handle_upload(), such as wp_handle_upload() or wp_handle_sideload().

Error reporting related to the file being moved will also be skipped.

Props ryan, Mte90.
Fixes #24603.