store: remove pointless pathjoiner parameter
We can stop pretending that we have to support anything else
than '/' for concatenating path elements anywhere.
Windows deals just fine with '/' in file paths and we already
have plenty of places which produce paths containing '/'
anyway when running on Windows.
Ancestors of 5
4 2 0
Ancestors of 6 and 5
3 4 2 1 0
Ancestors of 5 and 4
4 2 0
Descendants of 5
7 8
Descendants of 5 and 3
6 7 8
Descendants of 5 and 4
5 7 8