File (hook_file)

This is an experimental backport of Drupal 7's file.inc "hook_file" API to Drupal 6. Things work the same, except anywhere you would call a file_xyz function, you would call hook_file_xyz. Also, anywhere you would implement hook_file_xyz, you would instead implement hook_hook_file_xyz.

This would give modules the new functionality, and when ultimately upgrading, developers would replace the functions by simply changing all occurrences of "hook_file" to "file".