Merge diff always misses the `\ No newline at end of file` mark

[Danil Pristupov <danil@xxxxxxxx>]

For files with conflicts `git diff -- filename` always returns result
without the `No newline at end of file` mark.

I was able to reproduce this with all git versions on all platforms.

Steps to reproduce (macOS, 2.32.0 (Apple Git-132)):

```
git init
echo "line1\nline2" > eol.txt
echo -n "line1\nline2" > noeol.txt
git add .
git commit -m "initial"
git branch br1
echo "line11\nline2" > eol.txt
echo -n "line11\nline2" > noeol.txt
git add .
git commit -m "line1"
git checkout br1
echo "line12\nline2" > eol.txt
echo -n "line12\nline2" > noeol.txt
git add .
git commit -m "line2"
git merge master
git diff -- eol.txt > eol.diff
git diff -- noeol.txt > noeol.diff
```

Expected behavior: `noeol.diff` should have `\ No newline at end of file` mark

Actual behavior: Both `eol.diff` and `noeol.diff` have no `\ No
newline at end of file` mark

This is my first bug report. Please let me know if I'm missing something.