src/vs/base/common/extpath.ts/sanitizeFilePath
export function sanitizeFilePath(candidate: string, cwd: string): string {

	// Special case: allow to open a drive letter without trailing backslash
	if (isWindows && candidate.endsWith(':')) {
		candidate += sep;
	}

	// Ensure absolute
	if (!isAbsolute(candidate)) {
		candidate = join(cwd, candidate);
	}

	// Ensure normalized
	candidate = normalize(candidate);

	// Ensure no trailing slash/backslash
	if (isWindows) {
		candidate = rtrim(candidate, sep);

		// Special case: allow to open drive root ('C:\')
		if (candidate.endsWith(':')) {
			candidate += sep;
		}

	} else {
		candidate = rtrim(candidate, sep);

		// Special case: allow to open root ('/')
		if (!candidate) {
			candidate = sep;
		}
	}

	return candidate;
}