get emails from github users
myUser='ariya'
curl -s https://api.github.com/users/${myUser}/events/public | grep --no-group-separator -A1 email | sed 's/^\s\+//;s///' | tr -d '\n' | sed 's/"email": "/\n/g;s/"name"//g;s/[",]//g' | sort | uniq
recreate repository without commits history
git checkout --orphan latest_branch
git add -A
git commit -am "commit message"
git branch -D master
git branch -m master
git push -f origin master
you can use SVN to get only part of whole repo, e.g.
svn export https://github.com/grpc/grpc.git/trunk/examples/protos/