Bug 469450

SUMMARY
If a photo is read-only (e.g. -r--r--r--) but in a writable directory and digiKam attempts to write metadata to it, it will succeed (apparently by removing the file first). If I set "Write to XMP sidecar for read-only item only", it will acknowledge the photo is read-only by creating the sidecar, but it will still overwrite the original. If I make the directory read-only, the photo is protected, but digiKam cannot create sidecars. It can, however, modify them, once they exist.

STEPS TO REPRODUCE
1. Create a read-only photo in a writable directory
2. Make sure Metadata>Sidecars>Write to sidecar files is enabled
3. Make sure Metadata>Sidecars>Write to XMP sidecar for read-only item only is selected
4. Make sure Metadata>Rotation>Rotate by changing the content if possible is selected
5. Make sure Metadata>Rotation>Write flag to metadata if possible is enabled (I assume this is necessary to achieve the expected result, but it is not necessary to reproduce the observed result)
6. Rotate the photo

OBSERVED RESULT
The photo is rotated by replacing the read-only file with a modified one and an XMP sidecar is created

EXPECTED RESULT
The photo is rotated by setting a flag in the metadata, which is written to an XMP sidecar

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.27.4
KDE Frameworks Version: 5.105.0
Qt Version: 5.15.9

ADDITIONAL INFORMATION
As a workaround, I've made digiKam create sidecars for the photos I'm protecting, restored those photos from a backup, then made those photos and their parent directories read-only. I can now manage metadata in the sidecar without modifying the photo.