regression when comparing images with alpha to image without alpha with -alpha off

[josch]

ImageMagick version

6.9.12-84-33-gd49d6b227

Operating system

Linux

Operating system, version and so on

Debian bookworm

Description

When comparing attached images before commit d49d6b227a128aa0f9b4b0f2e2c697d44ac6dc65, they compared as equal. Starting with commit d49d6b227a128aa0f9b4b0f2e2c697d44ac6dc65, they appear as different. Bug or feature?

Steps to Reproduce

compare -metric AE -alpha off working.orig.jpg working.gs.png null:

Images

[urban-warrior]

We get a "Not a JPEG file" for the working original. Resolve this issue so we can reproduce the issue in our local environment.

[josch]

$ identify working.orig.jpg
working.orig.jpg JP2 60x60 60x60+0+0 8-bit sRGB 0.000u 0:00.001
$ file --mime working.orig.jpg
working.orig.jpg: image/jp2; charset=binary
$ file working.orig.jpg
working.orig.jpg: JPEG 2000 Part 1 (JP2)

I downloaded the version from this issue. md5sum should be 8e824e6e06227579ae0055eb392ca91c All tools above say that it's of jpeg type.