Created attachment 172240 [details]
A script to make the bug better reproduceable

SUMMARY
I re encoded my Movie collection to make some space on my external hard drive. The re encoded Videos were on another drive. So I ended upon with the following:
- The Directory with the original Video files on my external drive. Size: 400GB
- The Directory with the re encoded files on another drive (same filenames). Size: 285GB
- 125GB free space on my external drive
But when I wanted to copy the re encoded files to my external drive, Dolphin refuses to copy the files, because it doesn't have enough space. It didn't ask me if I want to override the old files.

STEPS TO REPRODUCE
1. Have Directory A
2. Have Directory B on another Drive
3. Directory B should have files with the exact Names (but smaller) as Directory A
4. The drive of Directory A should have less free space than the size of Directory B
5. Copy all files from Directory B to Directory A

To make this easier to reproduce I have attached a little script. Just run the script and try to copy test.bin from /tmp/bugdemo/b to /tmp/bugdemo/a.

OBSERVED RESULT
Dolphin claims there is not enough space.

EXPECTED RESULT
Dolphin should ask if I want to overwrite the files. As the files in B are smaller as in A, I should have more free space at the end of the overwriting.