When autorotating photos using an external program, digikam does not pick up new setting of EXIF orientation flag (or absence thereof)

[AlainKnaff]

When I visit a photo folder in digikam, and then auto-rotate the photos using imagemagick (convert -auto-orient myphoto.jpg myphoto.jpg), then digikam shows it rotated twice (just as if the file data had been rotated, and the EXIF tag was still present). For example, if the photo was initially rotated right, it will now be shown rotated left, rather than upright.
Jhead shows that such photos no longer have any EXIF orientation flag at all.

No matter of refresh, F5, clear thumbnails seems to convince digikam to take another look at the EXIF header to clear its cached copy of rotation flag.

The only thing that helps is to do Image->Adjust Exif Orientation Flag->Normal on each concerned photo individually.

1) root@hitchhiker:~# lsb_release -rd
Description: Ubuntu 14.04.4 LTS
Release: 14.04
2) root@hitchhiker:~# apt-cache policy digikam
digikam:
  Installed: 4:3.5.0-0ubuntu10
  Candidate: 4:3.5.0-0ubuntu10
  Version table:
 *** 4:3.5.0-0ubuntu10 0
        500 http://be.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
        100 /var/lib/dpkg/status

3) What I expected to happen

Even when an external program modifies the photo, digikam should (eventually) pick up the changes. It does pick up the changes within the bitmapped data after all.
Even without autodetection of the change, I'd expect that explicit refresh or clearing of thumbnails would do its job. Digikam's caching shouldn't be so damn stubborn.

4) What happened instead

There seems to be no way to cause digikam to re-read the orientation flag in the Exif header, short of visiting each affected picture individually and do Image->Adjust Exif Orientation Flag->Normal

P.S. I do know that digikam has its own autorotation function (Image->Autorotate/Flip using Exif Information), but for some reason this is *much* slower than using imagemagick...