"new-sources" should not be mentioned in basic documentation. These should be added via means of "fedpkg import package.srpm".
The workflow for new package is then:
~~~
$ fedpkg import mypackage.srpm
$ git commit -m "initial import"
~~~
and for updated package:
~~~
$ git add -u
$ fedpkg clog
$ git commit -F clog
$ fedpkg import updated.srpm
$ git commit --am
~~~
This way, the question if the file is stored in lookaside cache or git is done by fedpkg. Also please note that the "import" command removes patches which are not used any longer (not sure if it adds new patches ...).