appendPath/resolvePath drop trailing slashes and swallow excess '..' segments

[elharo]

Summary

The SCM-path normalization in ModelInheritanceAssembler has edge-case inaccuracies.

src/main/java/org/apache/maven/plugin/resources/remote/ModelInheritanceAssembler.java:548-616

protected String appendPath(String parentPath, String childPath, String pathAdjustment, boolean appendPaths) {
    ...
    return cleanedPath + resolvePath(uncleanPath);
}

private static String resolvePath(String uncleanPath) {
    LinkedList<String> pathElements = new LinkedList<>();
    StringTokenizer tokenizer = new StringTokenizer(uncleanPath, "/");
    while (tokenizer.hasMoreTokens()) {
        String token = tokenizer.nextToken();
        switch (token) {
            case "": break;
            case "..":
                if (pathElements.isEmpty()) {
                    // FIXME: somehow report to the user that there are too many '..' elements.
                    // For now, ignore the extra '..'.
                } else {
                    pathElements.removeLast();
                }
                break;
            default:
                pathElements.addLast(token);
                break;
        }
    }
    ...
}

Problems

1. Excess .. segments are silently ignored (there is a // FIXME acknowledging this) — a parent SCM URL with too many .. yields a path that does not match what the user wrote, with no warning.
2. Trailing slashes are dropped: http://x/repo/ + child becomes http://x/repo/child (arguably fine), but a bare http://x/repo/ (no child) normalizes to http://x/repo, changing the URL.
3. "" tokens (double slashes //) are silently removed, which can collapse URLs that legitimately contain them.

Impact

Inherited scm connection/url values in supplemental models can be subtly wrong for unusual parent URLs, producing checkout paths that differ from the source repository layout.

Suggested fix

Move to a well-tested path normalizer (e.g. java.nio.file.Paths/URI handling, or plexus-utils PathTool) and decide explicitly how to handle excess .., trailing slashes, and empty segments; emit a warning instead of silently dropping path elements.