feat: Reselect existing contributions when updating a user

lib/contributors/prompt.js

@@ -29,8 +29,27 @@ function getQuestions(options, username, contributions) {
     name: 'contributions',
     message: 'What are the contribution types?',
     when: !contributions,
+    default: function (answers) {
+      // default values for contributions when updating existing users
+      answers.username = answers.username || username;
+      return options.contributors
+        .filter((entry) => entry.login.toLowerCase() === answers.username.toLowerCase())
+        .reduce((allEntries, entry) => allEntries.concat(entry.contributions), []);
+    },
     choices: contributionChoices(options),
-    validate: input => input.length ? true : 'Use space to select at least one contribution type.'
+    validate: function (input, answers) {
+      answers.username = answers.username || username;
+      var previousContributions = options.contributors
+        .filter((entry) => entry.login.toLowerCase() === answers.username.toLowerCase())
+        .reduce((allEntries, entry) => allEntries.concat(entry.contributions), []);
+
+      if (!input.length) {
+        return 'Use space to select at least one contribution type.';
+      } else if (_.isEqual(input, previousContributions)) {
+        return 'Nothing changed, use space to select contribution types.';
+      }
+      return true;
+    }
   }];
 }