update dialog.showOpenDialog to promisified

packages/server/lib/gui/dialog.coffee

@@ -15,10 +15,7 @@ module.exports = {
       properties: ["openDirectory"]
     }
 
-    new Promise (resolve, reject) ->
-      dialog.showOpenDialog props, (paths = []) ->
-        process.nextTick ->
-          ## return the first path since there can only ever
-          ## be a single directory selection
-          resolve(paths[0])
+    dialog.showOpenDialog(props)
+    .then ({ filePaths }) ->
+      return filePaths[0]
 }

packages/server/test/unit/gui/dialog_spec.coffee

@@ -7,7 +7,9 @@ Windows = require("#{root}../lib/gui/windows")
 describe "gui/dialog", ->
   context ".show", ->
     beforeEach ->
-      @showOpenDialog = electron.dialog.showOpenDialog = sinon.stub()
+      @showOpenDialog = electron.dialog.showOpenDialog = sinon.stub().resolves({
+        filePaths: []
+      })
 
     it "calls dialog.showOpenDialog with args", ->
       dialog.show()
@@ -16,13 +18,13 @@ describe "gui/dialog", ->
       })
 
     it "resolves with first path", ->
-      @showOpenDialog.yields(["foo", "bar"])
+      @showOpenDialog.resolves({
+        filePaths: ["foo", "bar"]
+      })
 
       dialog.show().then (ret) ->
         expect(ret).to.eq("foo")
 
     it "handles null paths", ->
-      @showOpenDialog.yields(null)
-
       dialog.show().then (ret) ->
         expect(ret).to.eq(undefined)