feat(utils): add uniqueFilename helper with -2 collision suffix

src/utils/uniqueFilename.ts

@@ -0,0 +1,21 @@
+export const uniqueFilename = ({
+  basename,
+  extension,
+  existingPaths,
+  directory
+}: {
+  basename: string
+  extension: string
+  existingPaths: string[]
+  directory: string
+}): string => {
+  const prefix = directory ? `${directory}/` : ""
+  const candidate = (n: number) =>
+    n === 1 ? `${basename}${extension}` : `${basename}-${n}${extension}`
+  const taken = new Set(existingPaths)
+  let n = 1
+  while (taken.has(`${prefix}${candidate(n)}`)) {
+    n = n === 1 ? 2 : n + 1
+  }
+  return candidate(n)
+}