Default unityVersion to auto to use ProjectSettings/ProjectVersion.txt (#162) (#188)

src/model/unity-versioning.js

@@ -0,0 +1,33 @@
+import * as core from '@actions/core';
+import * as fs from 'fs';
+import * as path from 'path';
+
+export default class UnityVersioning {
+  static get versionPattern() {
+    return /20\d{2}\.\d\.\w{3,4}|3/;
+  }
+
+  static determineUnityVersion(projectPath, unityVersion) {
+    if (unityVersion === 'auto') {
+      return UnityVersioning.read(projectPath);
+    }
+    return unityVersion;
+  }
+
+  static read(projectPath) {
+    const filePath = path.join(projectPath, 'ProjectSettings', 'ProjectVersion.txt');
+    if (!fs.existsSync(filePath)) {
+      core.warning(`Could not find "${filePath}", keeping unityVersion as "auto"`);
+      return 'auto';
+    }
+    return UnityVersioning.parse(fs.readFileSync(filePath, 'utf8'));
+  }
+
+  static parse(projectVersionTxt) {
+    const matches = projectVersionTxt.match(UnityVersioning.versionPattern);
+    if (!matches || matches.length === 0) {
+      throw new Error(`Failed to parse version from "${projectVersionTxt}".`);
+    }
+    return matches[0];
+  }
+}