Disable jest watch mode when --coverage flag is present [#1207]

[BenoitAverty]

This PR adds the enhancement described in #1207.

I just added this condition to the addition of the '--watch' flag in the test script. I tested this on my computer and it seems to do the trick, i'm guessing the rest is handled by Jest (make all the tests run when not in watch mode, versus only run tests modified since last commit when watch mode is active).

If there's something I forgot, please let me know.

Also I ran the tasks/e2e.sh script, and it hangs on line 181
npm run test -- --watch=no because it does, in fact, run in watch mode. You have to press 'q' for the script to continue. Is this normal or a regression I introduced ? This seems to be true even on master...

Finally, is there something to add to test the new behavior?

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[gaearon]

Does this work when I pass more than one flag?

npm test -- --coverage App

Not sure it makes any sense, it's just that I don't remember how argv works.

[BenoitAverty]

In most languages, argv is an array of strings, which is the command line split on each space. In your case it's [ '--coverage', 'App' ], so it works as expected (I just tested it on my machine)

[gaearon]

Thank you!