Plugins repositores should have the plugin contents in their root. Like you have it now, developers can't clone your plugin into their moodle.git checkout. The expected workflow for admins and developers using git as the source for their adminer should be:

# cd /path/to/moodle/dirroot

# cd local

# git clone git@github.com:grabs/moodle-local_adminer.git adminer

which creates the adminer folder with the plugin contents.

Also, you have the master branch empty. Maybe at least a README.md file with the description of the repository structure would help.