feat: read from all known files if not specified

src/utils.ts

@@ -1,4 +1,4 @@
-import { warning } from "@actions/core";
+import { debug, warning } from "@actions/core";
 import { existsSync, readFileSync } from "node:fs";
 import { join, basename } from "node:path";
 
@@ -25,12 +25,25 @@ const FILE_VERSION_READERS = {
   ".bumrc": (content: string) => content,
 };
 
-export function readVersionFromFile(file: string): string | undefined {
+export function readVersionFromFile(
+  files: string | string[]
+): string | undefined {
   const cwd = process.env.GITHUB_WORKSPACE;
   if (!cwd) {
     return;
   }
 
+  if (!files) {
+    warning("No version file specified, trying all known files.");
+    readVersionFromFile(Object.keys(FILE_VERSION_READERS));
+    return;
+  }
+
+  if (!Array.isArray(files)) files = [files];
+
+  for (const file of files) {
+    debug(`Reading version from ${file}`);
+
     const path = join(cwd, file);
     const base = basename(file);
 
@@ -44,4 +57,5 @@ export function readVersionFromFile(file: string): string | undefined {
       const { message } = error as Error;
       warning(`Failed to read ${file}: ${message}`);
     }
+  }
 }