in report-builder/src/jetbrains/coverage/report/impl/IOUtil.java [135:148]
public static String makeRelative(@NotNull final File base, @NotNull final File path) {
if (base.equals(path)) return ".";
final String sFind = path.getPath();
final String sBasePath = base.getPath();
if (!path.getPath().startsWith(sBasePath + File.separatorChar)) {
final String next = makeRelative(base.getParentFile(), path);
if (".".equals(next)) return "..";
return "../" + next;
} else {
return sFind.substring(sBasePath.length() + 1);
}
}