fix(adapter): fix package.json spaces being removed

To fix windows issues in the json npm package, we switched to using JSON.parse and writeFileSync. In
this switch I forgot about package.json formatting. Luckily @sindresorhus has already created
detect-indent so I've switched to using that.

Closes #72

package.json

@@ -59,6 +59,7 @@
     "chalk": "1.1.1",
     "cz-conventional-changelog": "1.1.4",
     "dedent": "0.6.0",
+    "detect-indent": "4.0.0",
     "find-node-modules": "1.0.1",
     "glob": "5.0.15",
     "gulp": "3.9.0",

src/commitizen/adapter.js

@@ -2,6 +2,7 @@ import path from 'path';
 import fs from 'fs';
 import findNodeModules from 'find-node-modules';
 import _ from 'lodash';
+import detectIndent from 'detect-indent';
 
 import {isFunction} from '../common/util';
 
@@ -39,13 +40,15 @@ function addPathToAdapterConfig(sh, cliPath, repoPath, adapterNpmName) {
   };
 
   let packageJsonPath = path.join(getNearestProjectRootDirectory(), 'package.json');
-  let packageJsonString = fs.readFileSync(packageJsonPath);
+  let packageJsonString = fs.readFileSync(packageJsonPath, 'utf-8');
+  // tries to detect the indentation and falls back to a default if it can't
+  let indent = detectIndent(packageJsonString).indent || '  ';
   let packageJsonContent = JSON.parse(packageJsonString);
   let newPackageJsonContent = '';
   if(_.get(packageJsonContent,'config.commitizen.path') !== adapterNpmName) {
     newPackageJsonContent = _.merge(packageJsonContent, commitizenAdapterConfig);
   }
-  fs.writeFileSync(packageJsonPath, JSON.stringify(newPackageJsonContent));
+  fs.writeFileSync(packageJsonPath, JSON.stringify(newPackageJsonContent, null, indent));
 }
 
 /**