The behavior of prop=imageinfo with redirects, particularly redirects in foreign repos such as Commons, has always been a bit strange and confusing. Depending on the source of the file, sometimes &redirects=1 is needed in the query to get the imageinfo for a redirect and sometimes this is done regardless.

Recent changes to the file repository backend code will cause prop=imageinfo to now always return the info for the target file, even when querying a redirect without specifying "&redirects=1" in the query. A new iiprop is also available, iiprop=canonicaltitle, to indicate the title associated with the file info itself.

These changes will be deployed to WMF sites with 1.23wmf7, see https://www.mediawiki.org/wiki/MediaWiki_1.23/Roadmap for the schedule.

A change is also being planned by Brian Wolff to change prop=imageinfo back in the other direction: file redirects would never be followed unless &redirects=1 is included. Feedback is welcome, particularly on edge cases that will need to be handled.

-- Brad Jorsch (Anomie) Software Engineer Wikimedia Foundation