relativeTo

import std.array : array;
import std.conv : to;
assert(PosixPath("/some/path").relativeTo(PosixPath("/")) == PosixPath("some/path"));
assert(PosixPath("/some/path/").relativeTo(PosixPath("/some/other/path/")) == PosixPath("../../path/"));
assert(PosixPath("/some/path/").relativeTo(PosixPath("/some/other/path")) == PosixPath("../../path/"));

assert(WindowsPath("C:\\some\\path").relativeTo(WindowsPath("C:\\")) == WindowsPath("some\\path"));
assert(WindowsPath("C:\\some\\path\\").relativeTo(WindowsPath("C:\\some\\other\\path/")) == WindowsPath("..\\..\\path\\"));
assert(WindowsPath("C:\\some\\path\\").relativeTo(WindowsPath("C:\\some\\other\\path")) == WindowsPath("..\\..\\path\\"));

assert(WindowsPath("\\\\server\\share\\some\\path").relativeTo(WindowsPath("\\\\server\\share\\")) == WindowsPath("some\\path"));
assert(WindowsPath("\\\\server\\share\\some\\path\\").relativeTo(WindowsPath("\\\\server\\share\\some\\other\\path/")) == WindowsPath("..\\..\\path\\"));
assert(WindowsPath("\\\\server\\share\\some\\path\\").relativeTo(WindowsPath("\\\\server\\share\\some\\other\\path")) == WindowsPath("..\\..\\path\\"));

assert(WindowsPath("C:\\some\\path").relativeTo(WindowsPath("D:\\")) == WindowsPath("C:\\some\\path"));
assert(WindowsPath("C:\\some\\path\\").relativeTo(WindowsPath("\\\\server\\share")) == WindowsPath("C:\\some\\path\\"));
assert(WindowsPath("\\\\server\\some\\path\\").relativeTo(WindowsPath("C:\\some\\other\\path")) == WindowsPath("\\\\server\\some\\path\\"));
assert(WindowsPath("\\\\server\\some\\path\\").relativeTo(WindowsPath("\\\\otherserver\\path")) == WindowsPath("\\\\server\\some\\path\\"));
assert(WindowsPath("\\some\\path\\").relativeTo(WindowsPath("\\other\\path")) == WindowsPath("..\\..\\some\\path\\"));

assert(WindowsPath("\\\\server\\share\\path1").relativeTo(WindowsPath("\\\\server\\share\\path2")) == WindowsPath("..\\path1"));
assert(WindowsPath("\\\\server\\share\\path1").relativeTo(WindowsPath("\\\\server\\share2\\path2")) == WindowsPath("\\\\server\\share\\path1"));
assert(WindowsPath("\\\\server\\share\\path1").relativeTo(WindowsPath("\\\\server2\\share2\\path2")) == WindowsPath("\\\\server\\share\\path1"));