Import React DevTools v4

[bvaughn]

This PR imports the entire React DevTools v4 git repository (with history). I will manually migrate open issues after this PR has landed.

Despite its size, this PR is almost entirely additive:

$git diff master --name-status | grep -v "A"       
M	.circleci/config.yml
M	.eslintignore
M	.gitignore
M	package.json
M	packages/react-debug-tools/src/ReactDebugHooks.js
M	packages/react-devtools-core/package.json
M	packages/react-devtools-inline/package.json
M	packages/react-devtools/package.json
M	scripts/flow/config/flowconfig
M	scripts/jest/config.build.js
M	scripts/jest/config.source-persistent.js
M	scripts/jest/config.source.js
M	scripts/jest/preprocessor.js
M	scripts/print-warnings/print-warnings.js
M	yarn.lock

Checklist

• Import (with history preserved)
• Delete ReactDebugHooks fork (and use react-debug-tools)
• Relocate unique dependencies to the appropriate package.json
• Automated tests
  • Make sure all DevTools tests pass
  • Make sure CI runs DevTools tests also
• Remove forked Flow types
• Add copyright header to all files
• Test builds and artifacts
  • react-devtools standalone app
  • react-devtools-core package
  • react-devtools-extensions (Chrome and Firefox)
  • react-devtools-inline package
  • react-devtools-shell test harness
• Update outdated README instructions
• Fix Now deployment script for demo shell

Folder structure

.
├── fixtures
│   ├── # (existing fixtures...)
│   └── devtools
│       ├── regression
│       └── standalone
└── packages
    ├── # (existing packages...)
    ├── react-devtools # Published to NPM
    ├── react-devtools-core # Published to NPM
    ├── react-devtools-extensions # Published to Chrome/Firefox stores
    │       ├── chrome
    │       ├── firefox
    │       └── shared
    ├── react-devtools-inline # Published to NPM
    ├── react-devtools-shared # Source for other DevTools packages
    └── react-devtools-shell # Dev app built with "react-devtools-inline"

Importing

The goal of this import is to preserve history from the DevTools v4 fork. Below are the steps I followed. Afterward, I verified that git log --follow worked as expected on imported files.

Prepare fork for merge

mkdir ~/Desktop/devtools-merge
cd ~/Desktop/devtools-merge

git init .
git commit -m "Initializing empty merge repo" --allow-empty  

git remote add -f fork git@github.com:bvaughn/react-devtools-experimental.git
git merge fork/master --allow-unrelated-histories

# Moved everything except "packages" into a new "extension" subdirectory
# to avoid merge conflicts with React repo folder structure

Import into React

cd ~/Documents/git/react

git remote add devtools-merge ~/Desktop/devtools-merge
git fetch devtools-merge

git checkout -b devtools-v4-merge
git merge --allow-unrelated-histories devtools-merge/master

git remote rm devtools-merge

[MichaelDeBoey]

🎉🎉🎉