Pass entry files to arguments of parcel cli

$ yarn run parcel a.js b.js

$ cat dist/parcel-manifest.json
{"a.js":"/a.js","b.js":"/b.js"}

$ yarn run parcel build a.js b.js
$ cat dist/parcel-manifest.json
{"a.js":"/a.js","b.js":"/b.js"}

Set package.json#source

package.json

{
  ...
  "source": ["a.js", "b.js"],
}

$ yarn run parcel serve
$ cat dist/parcel-manifest.json
{"a.js":"/a.js","b.js":"/b.js"}

$ yarn run parcel build
$ cat dist/parcel-manifest.json
{"a.js":"/a.js","b.js":"/b.js"}

Set package.json#targets

package.json

{
  ...
  "targets": {
    "a": {
      "source": "a.js"
    },
    "b": {
      "source": "b.js"
    }
  },
}

$ yarn run parcel serve
$ cat dist/parcel-manifest.json
{"a.js":"/a.js","b.js":"/b.js"}

$ yarn run parcel build
$ cat dist/a/parcel-manifest.json
{"a.js":"/a.js"}
$ cat dist/b/parcel-manifest.json
{"b.js":"/b.js"}