* Temporarily only do one pass

* Add types

* Generate two versions of pages

* Add code VSCode deleted

* Add dynamicBuildId option to __NEXT_DATA__

* Reduce amount of diff

* Make getPageFile code easier to read

* Minimize diff

* minimize diff

* Fix default value for dynamicBuildId

* Fix weird bug

* Fetch the head build id on client

* Move __selectivePageBuilding

* Add tests

* Remove _this

* Add console warning

* Added amp-toolbox-optimizer and added
optimizing AMP pages as dirty and clean

* Fix amp-optimizer breaking serverless build

* Exclude amp-toolbox-optimizer from serverless build

* Added check to make sure hybrid AMP pages
optimize cleanly during export

* Add check to make sure noDirtyAmp is applied

Replaced regenerator with async-to-promises

Replaces `import()` with `require` only for the testing environment.

Update tests to setup webdriver stuff in `jest-environment` and re-use one browser session instead of spawning one for each webdriver call to prevent creating too many BrowserStack sessions. 

`unfetch` ^4.0.0 is already used by `isomorphic-unfetch` so this simplifies the dependency tree a tiny bit.

Release notes
https://github.com/developit/unfetch/releases/tag/4.0.0
https://github.com/developit/unfetch/releases/tag/4.1.0

* Remove magic-string

* Add back input

* change if statement back

* Fix typo

* remomve useless import

More modules to follow.

* Remove hoist-non-react-statics from with-router

* Drop hoist-non-react-statics from package.json

* Break out client-navigation and rendering
test from basic test

* Try with parallelism dialed back to 3

* Update jest-junit for more compatible timings in CircleCI

* Bump to test timings

* Use filepath for suitename in jest-junit

* Store reports as artifacts

* Try using classname for timings

* Bump

* Remove reports from artifacts

* Inject the build ID after webpack runs

* add webpack sources types

* use webpack plugin instead

* reset file

* Skip source maps if none were provided
Co-Authored-By: NTimer <timer150@gmail.com>

While this is a nice feature it does filesystem operations to check if the resolved file matches the filesystem.

Fixes: #5481

Also added `HEADLESS` env var for local testing

More cleanup of terser-plugin.

Removes `rimraf` for a smaller custom lib

Benchmarks (in ms):
```
rimraf 1
518.536376
rimraf 2
416.112451
rimraf 3
451.905842
rimraf 4
525.117395
rimraf 5
434.230384
---- Average: 469.18ms
-----------
recursive delete 1
121.493979
recursive delete 2
130.335272
recursive delete 3
149.798316
recursive delete 4
182.184688
recursive delete 5
130.346207
--- Average: 142.83ms
```
`recursiveDelete` finishes in ~30% of the time it takes `rimraf` (3.3 times faster)

At request of @timneutkens I moved the `next-mdx` plugin from the next-plugins repo into Next.js. Also fixed small typo in README under setup.

We don't use a lot of the features of `glob`, so let's remove it in favor of a leaner approach using regex.

It's failing on windows and I have no idea why and don't own a windows machine 🤦🏼‍♂️

(Ignore some of the commits in here, I forgot to create the new branch before I started working)

* Add ncc taskfile

* Add ncc dep and pass options

* dev dep

* Make console output well behaved

* Fix bad rebase

Upgrades `standard` to major version 12

After talking with @timneutkens it was decided it'd be more streamlined to replace the onDemandEntries WebSocket with an alternative. Using the EventSource connection gives us these benefits over the WebSocket one:

- less code needed
- no extra server running
- no extra config for onDemandEntries