From 6ef88d640965032ba612d7dd935d6630f15098cc Mon Sep 17 00:00:00 2001
From: Robert Jackson <rjackson@linkedin.com>
Date: Tue, 15 Aug 2017 10:18:09 -0400
Subject: [PATCH 1/2] Add `--package-json-only` command line option.

---
 bin/ember-cli-update.js | 4 +++-
 src/args.js             | 5 +++++
 src/index.js            | 1 +
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/bin/ember-cli-update.js b/bin/ember-cli-update.js
index c9365b944..b896bb773 100755
--- a/bin/ember-cli-update.js
+++ b/bin/ember-cli-update.js
@@ -13,9 +13,11 @@ const argv = require('yargs')
 const from = argv['from'];
 const to = argv['to'];
 const ignoreConflicts = argv['ignore-conflicts'];
+const packageJsonOnly = argv['package-json-only'];
 
 emberCliUpdate({
   from,
   to,
-  ignoreConflicts
+  ignoreConflicts,
+  packageJsonOnly
 });
diff --git a/src/args.js b/src/args.js
index 3fa79240f..601a4b9f6 100644
--- a/src/args.js
+++ b/src/args.js
@@ -12,5 +12,10 @@ module.exports = {
     type: 'boolean',
     default: false,
     description: 'Handle merge conflicts yourself'
+  },
+  'package-json-only': {
+    type: 'boolean',
+    default: false,
+    description: 'Attempt to automatically merge package.json changes'
   }
 };
diff --git a/src/index.js b/src/index.js
index bc3eb4e01..18c76ae42 100644
--- a/src/index.js
+++ b/src/index.js
@@ -11,6 +11,7 @@ module.exports = function emberCliUpdate(options) {
   let from = options.from;
   let to = options.to;
   let ignoreConflicts = options.ignoreConflicts;
+  let packageJsonOnly = options.packageJsonOnly;
 
   let versions = JSON.parse(
     run('npm info ember-cli versions --json')

From d49962f4fdd86c75d57c4f2bef1add34bb50ab4b Mon Sep 17 00:00:00 2001
From: Robert Jackson <rjackson@linkedin.com>
Date: Tue, 15 Aug 2017 10:20:03 -0400
Subject: [PATCH 2/2] Add `auto-merge-package-json` utility function.

---
 package.json                   |  4 ++
 src/auto-merge-package-json.js | 76 ++++++++++++++++++++++++++++++++++
 src/index.js                   |  5 +++
 3 files changed, 85 insertions(+)
 create mode 100644 src/auto-merge-package-json.js

diff --git a/package.json b/package.json
index 0211161fc..9ac72c6d3 100644
--- a/package.json
+++ b/package.json
@@ -34,7 +34,11 @@
   "dependencies": {
     "debug": "^3.0.0",
     "git-diff-apply": "^0.2.0",
+    "got": "^7.1.0",
+    "rfc6902": "^1.3.0",
     "semver": "^5.4.1",
+    "sort-package-json": "^1.7.0",
+    "three-way-merger": "^0.2.0",
     "yargs": "^8.0.2"
   },
   "devDependencies": {
diff --git a/src/auto-merge-package-json.js b/src/auto-merge-package-json.js
new file mode 100644
index 000000000..baa31bcc7
--- /dev/null
+++ b/src/auto-merge-package-json.js
@@ -0,0 +1,76 @@
+'use strict';
+
+const fs = require('fs');
+const got = require('got');
+const sortPackageJson = require('sort-package-json');
+const ThreeWayMerger = require('three-way-merger');
+const rfc6902 = require('rfc6902');
+
+function clone(obj) {
+  return JSON.parse(JSON.stringify(obj));
+}
+
+function applyDependencyOperations(operations, source) {
+  operations.add.forEach((dep) => source[dep.name] = dep.version);
+  operations.remove.forEach((dep) => delete source[dep.name]);
+  operations.change.forEach((dep) => source[dep.name] = dep.version);
+}
+
+function mergeDependencyChanges(source, ours, theirs) {
+  let mergeOperations = ThreeWayMerger.merge({ source, ours, theirs });
+
+  // get a fresh copy so we don't mutate the passed in arg
+  let result = clone(ours);
+
+  applyDependencyOperations(mergeOperations.dependencies, result.dependencies);
+  applyDependencyOperations(mergeOperations.devDependencies, result.devDependencies);
+
+  return result;
+}
+
+function deleteDeps(input) {
+  delete input.dependencies;
+  delete input.devDependencies;
+}
+
+function mergeNonDependencyChanges(_source, _ours, _theirs) {
+  let source = clone(_source);
+  let ours = clone(_ours);
+  let theirs = clone(_theirs);
+
+  deleteDeps(source);
+  deleteDeps(ours);
+  deleteDeps(theirs);
+
+  let fromSourceToOurs = rfc6902.createPatch(source, ours);
+
+  rfc6902.applyPatch(theirs, fromSourceToOurs);
+
+  return theirs;
+}
+
+module.exports = function autoMergePackageJson(projectType, from, to) {
+  let projectKeyword = projectType === 'app' ? 'new' : 'addon';
+  let remoteUrl = `https://rawgit.com/ember-cli/ember-${projectKeyword}-output`;
+
+  return Promise.all([
+    got(`${remoteUrl}/${from}/package.json`, { json: true }),
+    got(`${remoteUrl}/${to}/package.json`, { json: true }),
+  ])
+    .then((results) => {
+      let fromPackageJson = results[0].body;
+      let toPackageJson = results[1].body;
+      let currentPackageJson = JSON.parse(fs.readFileSync('package.json', { encoding: 'utf-8' }));
+
+      let mergedDependenciesPackageJson = mergeDependencyChanges(fromPackageJson, currentPackageJson, toPackageJson);
+      let mergedOtherPackageJson = mergeNonDependencyChanges(fromPackageJson, currentPackageJson, toPackageJson);
+
+      let finalMergedPackageJson = mergedOtherPackageJson;
+      finalMergedPackageJson.dependencies = mergedDependenciesPackageJson.dependencies;
+      finalMergedPackageJson.devDependencies = mergedDependenciesPackageJson.devDependencies;
+
+      let sortedPackageJson = sortPackageJson(finalMergedPackageJson);
+
+      fs.writeFileSync('package.json', JSON.stringify(sortedPackageJson, null, 2) + '\n', { encoding: 'utf-8' });
+    });
+}
diff --git a/src/index.js b/src/index.js
index 18c76ae42..132723bfb 100644
--- a/src/index.js
+++ b/src/index.js
@@ -32,6 +32,11 @@ module.exports = function emberCliUpdate(options) {
 
   let remoteUrl = `https://github.com/ember-cli/ember-${projectKeyword}-output`;
 
+  if (packageJsonOnly) {
+    const autoMergePackageJson = require('./auto-merge-package-json');
+    return autoMergePackageJson(projectType, startTag, endTag);
+  }
+
   return gitDiffApply({
     remoteUrl,
     startTag,