make the exclude file optionally fail when being read with exclude_file_required

Author: GrantBirki

src/functions/exclude.js

@@ -5,6 +5,7 @@ import ignore from 'ignore'
 export class Exclude {
   constructor() {
     this.path = core.getInput('exclude_file')
+    this.required = core.getBooleanInput('exclude_file_required')
     this.gitTrackedOnly = core.getBooleanInput('use_gitignore')
 
     // initialize the exclude array
@@ -13,8 +14,17 @@ export class Exclude {
     // read the exclude file if it was used
     if (this.path && this.path !== '') {
       core.debug(`loading exclude_file: ${this.path}`)
-      this.ignore.add(readFileSync(this.path, 'utf8').toString())
-      core.debug(`loaded custom exclude patterns`)
+      try {
+        this.ignore.add(readFileSync(this.path, 'utf8').toString())
+        core.debug(`loaded custom exclude patterns`)
+      } catch (error) {
+        if (this.required === true) {
+          core.setFailed(`error reading exclude_file: ${this.path}`)
+          return new Error(`error: ${error}`)
+        }
+
+        core.info(`exclude_file was not found, but it is not required - OK`)
+      }
     }
 
     // if gitTrackOnly is true, add the git exclude patterns from the .gitignore file if it exists