API: very rudimentary implementation of _v. We'll have a proper

implementation in APIv2, but this will help with performance for rewrite
& mobile

src/controllers/api.coffee

@@ -34,6 +34,7 @@ api.auth = (req, res, next) ->
   User.findOne {_id: uid, apiToken: token}, (err, user) ->
     return res.json(500, {err}) if err
     return res.json(401, NO_USER_FOUND) if _.isEmpty(user)
+    res.locals.wasModified = +user._v isnt +req.query._v
     res.locals.user = user
     next()
 
@@ -423,6 +424,8 @@ api.batchUpdate = (req, res, next) ->
   async.series actions, (err) ->
     res.json = oldJson; res.send = oldSend
     return res.json(500, {err}) if err
-    res.json 200, user
+    response = user.toJSON()
+    response.wasModified = res.locals.wasModified
+    res.json 200, response
     console.log "Reply sent"
 

src/models/user.coffee

@@ -6,9 +6,12 @@ _ = require('lodash')
 UserSchema = new Schema(
 
   _id: {type: String, 'default': helpers.uuid}
-
   apiToken: {type: String, 'default': helpers.uuid}
 
+  # We want to know *every* time an object updates. Mongoose uses __v to designate when an object contains arrays which
+  # have been updated (http://goo.gl/gQLz41), but we want *every* update
+  _v: {type: Number, 'default': 0}
+
   achievements:
     originalUser: Boolean
     helpedHabit: Boolean
@@ -181,6 +184,7 @@ UserSchema.methods.toJSON = () ->
 # Custom setter/getter virtuals?
 UserSchema.pre 'save', (next) ->
   @markModified('tasks')
+  @._v++ #our own version incrementer
   next()
 
 module.exports.schema = UserSchema