Compare .deb file to filesystem

[Jules Bean <jules@jellybean.co.uk>]

This would be very easy to implement, so I thought I'd see if anyone
else has already done it.

I'd like a utility which takes a .deb file, another version of which
is already installed. It checks (presumably by file size and md5sum)
for all differences between the files on the file system, and the
files in the deb, and lists them.

I know debsums does part of this job, but AIUI only if the .deb
contains md5sums information.

This would be a useful tool for a maintainer with a complex package (I
have an internal one here in mind) which he has been forced to edit
the files 'in-place' to fix problems, and wishes to get a list of all
files he edited.

Does this exist?

Jules