Prettier v2 has the following breaking changes:
* enforces spaces between `function` and params
* enforces trailing commas by default

This is needed in order to use `globalThis`, see #1894.
It also made it possible to remove some old polyfills and fallbacks.

Parser tests are not used anymore, since the parser is
now living in a separate package.

By adding the `.js`-extension to the bin-file, IDEs will
know that js code-highlighting should be applied to the
file, which makes it easier for devs to read the code.

Second part of reorganizing and cleaning up test-folders.

First part of reorganizing and cleaning up test-folders.

Extracts the parser to `@handlebars/parser`, where it can be shared
between different implementations. This means that e.g. Glimmer/Ember
will be able to iterate on new features without forcing Handlebars to
adopt them immediately, and vice versa. All implementors will be able to
absorb changes as it makes sense for them.

- demonstrates the regression

- Add spec/tmp directory with .gitkeep file to indicate the folder is intentional
- Add the folder contents to .gitignore
- Use this folder to output the sourcemap file during bin tests. This file is a sideeffect of the main test

Per comment by @ErisDS on the GitHub PR:
#1666 (comment)

- adds full unit tests for all cli options
- demonstrates that nothing changes between minimist and yargs except a minor order change in the --help text
- proves b9c4b25 works the same as before

Co-authored-by: fabb <fabb@users.noreply.github.com>

closes #1644

- this allows the test to be run in a debugger
  without the complete PATH

… callbacks

- use es2017 rules as NodeJS supports it today
- add "prefer-const"

The main reason is that neo-async takes a lot less space due to the missing lodash-dependency.
The other is speed.

closes #1431

Closes #1233

- Handle path-separators properly. Use "path.sep" instead of "/".
  Or use "require.resolve()" if possible
- Use "execFile" instead of "exec" to run the Handlebars executable.
  This prevents problems due to (missing) shell escaping.
- Use explicit call to "node" in order to run the executable on Windows.
- Add "appveyor"-CI in order to run regular tests on Windows.

(cherry picked from commit 275ab37)

Fixes #1233

NodeJS files cannot be executed directly on Windows.

Fixes #1331

Due to the way, "bin"-files are distributed into the node_modules/.bin
directory on Windows, the task "test:cov" did not work on Windows.
This commit uses the node-script directly.

This hasn’t been running and is horribly out of date.