fix(mergedeep): hasChanges for empty source and non-empty target

Fix for empty collaborators config not removing excess members.
Using config `collaborators: []` this fix makes sure that manually
added collaborators are removed.

lib/mergeDeep.js

@@ -163,7 +163,10 @@ class MergeDeep {
       modifications = this.removeEmptyAndNulls(modifications, key)
       additions = this.removeEmptyAndNulls(additions, key)
     }
-    return ({ additions, modifications, hasChanges: !this.isEmpty(additions) || !this.isEmpty(modifications) })
+    let hasChanges = !this.isEmpty(additions) || !this.isEmpty(modifications)
+    // Indicate changes when source is empty and target is not
+    hasChanges |= this.isEmpty(source) && !this.isEmpty(target)
+    return ({ additions, modifications, hasChanges })
   }
 
   validateOverride (key, baseconfig, overrideconfig) {

test/unit/lib/mergeDeep.test.js

@@ -1013,3 +1013,15 @@ it('CompareDeep produces correct result for arrays of named objects', () => {
 
   expect(result.modifications.teams).toEqual(['developers'])
 })
+
+it('CompareDeep result has changes when source is empty and target is not', () => {
+  const ignorableFields = []
+  const mergeDeep = new MergeDeep(log, ignorableFields)
+  const target = [
+      { username: 'unwanted-collaborator' }
+    ]
+  const source = []
+  const result = mergeDeep.compareDeep(target, source)
+
+  expect(result.hasChanges).toBeTruthy()
+})