There’s a common tool included in Hadoop that also has a `yarn` command,
which created issues for users who had Hadoop installed:
* #1257
* #1363
Yarn also installs the command under `yarnpkg` alias (added in
cefa9a368d)
so we can use `yarnpkg` instead of `yarn` to make it more reliable.
This has no effect on users who don't have Hadoop installed, but those
who have won't see errors from falsely detecting Hadoop Yarn as Yarn
the package manager, and they can now also install Yarn to make use of
our Yarn support without the Hadoop Yarn interfering.
In the `create-react-app` command, try to install packages using Yarn.
If Yarn is not installed, use npm instead.
In `react-scripts`, detect if the project is using Yarn by checking if
a `yarn.lock` file exists. If the project is using Yarn, display all
the instructions with Yarn commands and use Yarn to install packages
in `init` and `eject` scripts.
* Forked react-scripts should retain the binary name
* Forked react-scripts should retain the binary name -- fixed issue with regex
* Forked react-scripts should retain the binary name -- fixed style nit
