The two following medium articles are explaining the best strategy
How to export clean . svg icons with Sketch
Tips for exporting vector assets from Sketch to AndroidDesign best practices for Android mobile App (with SketchApp)
In a nutshell: Avoid using… more
HEAD is a pointer to a commit (usually master) so when you checkout your repository the commit which HEAD points at will be checked out. Usually you'd want it if when checking out you want a different branch or tag to be checked out… more