add envinfo package, —info flag

[tabrindle]

I realize the file says not to modify the createReactApp.js, but a better way to do this did not occur to me. If there is a better way, I am certainly open to it.

To help the issue process and better narrow down environment and version issues, I have added create-react-app --info which should print the following:

Environment: OS: macOS High Sierra 10.13 Node: 8.6.0 Yarn: 1.2.1 npm: 5.5.1 Watchman: 4.9.0 Packages: (wanted => installed) react: ^16.0.0 => 16.0.0 react-dom: ^16.0.0 => 16.0.0 react-scripts: 1.0.17 => 1.0.17 

[gaearon]

Let's also check for duplicate react / react-dom in the tree?

[tabrindle]

That's a great idea. Will add.

[tabrindle]

With the new option--duplicates on envinfo, duplicates will now also show in parentheses.

Environment: OS: macOS High Sierra 10.13 Node: 8.6.0 Yarn: 1.2.1 npm: 5.5.1 Watchman: 4.9.0 Packages: (wanted => installed) react: 16.0.0 => 16.0.0 (15.6.2) 

You can actually test this in an existing CRA with npx envinfo@3.8.0 --packages "react,react-dom,react-scripts" --noNativeIDE --duplicates

[bondz]

Still doesn't have a react-scripts-dangerous version to test out. cc @Timer

The test failure isn't related to this PR.

[tabrindle]

Is there anything I can do to trigger the test build for react-scripts-dangerous?

[bondz]

Ping @Timer

[Timer]

I shut off the react-scripts-dangerous bot as I started to get quite expensive.

Cost $6 for two months, then randomly went wild -- no clue what happened here. 😅

[bondz]

Whaat! That's a bummer @Timer. Was really helpful but doesn't make sense if it costs you that much. Thanks for building it. Maybe we can find someone willing to host it later.

[Timer]

I think there was just some bug that caused the lambdas to run rampant; eventually when I have some free time I'll adjust it to prevent this from happening again.

[gaearon]

Looks like a good start. Let's get this in and iterate.

[gaearon]

This is out.
Can you send a PR to issue template to ask for this info please?

[bondz]

See #3797