In section_xxx.xml files (other than section_master.yml), it should be good to print a warning when "git_commit" field is set to master. Because this case is not logical and most of the time is due to an incorrect copy/paste of a yml section file coming from master.
Here an example with section_flounder.yml file :
url_fetch : "GERRIT_FETCH"
git_commit : "flounder"
name: Developers Guides
git_commit : "master" <<<< should generate a warning