On a slight tangent (no need to eject and works in develop),
this may be of help to other folk looking to add their current git commit SHA into their index.html as a meta-tag by adding:
REACT_APP_GIT_SHA=`git rev-parse --short HEAD`
to the build script in the package.json and then adding (note it MUST start with REACT_APP… or it will be ignored):
<meta name="ui-version" content="%REACT_APP_GIT_SHA%">
into the index.html in the public folder.
Within react components, do it like this:
<Component>{process.env.REACT_APP_GIT_SHA}</Component>