Possible regression for the (fixed) meta data part

[lightwisephoto]

Possible regression for the (fixed) meta data part here:

When you rotate a RAW file like .NEF you get asked if you wanted to save changes (correct) and are then prompted for a new file name (which is incorrect, since we could write meta data changes on their own).

mCurrentImage->saveMetaData(); would be sufficient. But it is not reached since DkUtils::isSavable(mCurrentImage->fileInfo().fileName()) is false because we can't write file contents of RAW files (nevertheless we are able to write meta data).

Originally posted by @lightwisephoto in #837 (comment)