drop anywhere in folder

website/src/lib/components/explorer/state.svelte.ts

@@ -33,6 +33,12 @@ function isSeparator(char: string | undefined) {
     return char === '/' || char === '\\';
 }
 
+/** The folder that holds `path`. */
+export function parentOf(path: string): string {
+    const index = Math.max(path.lastIndexOf('/'), path.lastIndexOf('\\'));
+    return index > 0 ? path.slice(0, index) : path;
+}
+
 /** Whether `path` is `folder` or something in it. */
 export function isWithin(path: string, folder: string): boolean {
     return path === folder || (path.startsWith(folder) && isSeparator(path[folder.length]));