Initial work for upgrade feature

libs/git.js

@@ -186,7 +186,7 @@ module.exports = {
       })
     })
     .catch((err) => {
-      winston.error('[' + PROCNAME + '][GIT] Unable to push changes to remote!')
+      winston.error('[' + PROCNAME + '.Git] Unable to push changes to remote!')
       throw err
     })
   },

libs/system.js

@@ -0,0 +1,42 @@
+'use strict'
+
+const Promise = require('bluebird')
+const https = require('follow-redirects').https
+const fs = Promise.promisifyAll(require('fs-extra'))
+const path = require('path')
+const tar = require('tar')
+const zlib = require('zlib')
+const _ = require('lodash')
+
+module.exports = {
+
+  _remoteFile: 'https://github.com/Requarks/wiki/releases/download/{0}/wiki-js.tar.gz',
+  _installDir: '',
+
+  install (targetTag) {
+    let self = this
+
+    self._installDir = path.resolve(ROOTPATH, appconfig.paths.data, 'install')
+
+    return fs.ensureDirAsync(self._installDir).then(() => {
+      let remoteURL = _.replace(self._remoteFile, '{0}', targetTag)
+
+      return new Promise((resolve, reject) => {
+        https.get(remoteURL, resp => {
+          if (resp.statusCode !== 200) {
+            return reject(new Error('Remote file not found'))
+          }
+
+          resp.pipe(zlib.createGunzip())
+          .pipe(tar.Extract({ path: self._installDir }))
+          .on('error', err => reject(err))
+          .on('end', () => {
+            resolve(true)
+          })
+        })
+      }).then(() => {
+
+      })
+    })
+  }
+}