This gist copies the last N commits from sourceBranch to destBranch.

copyLastNCommits.sh

sourceBranch=$1
destBranch=$2
numLastCommitsOnPrivateBranch=$3
git checkout ${sourceBranch}
startingCommit=`git rev-parse HEAD`
endingCommit=`git rev-parse HEAD~${numLastCommitsOnPrivateBranch}`
git checkout ${destBranch}
ontoValue=`git rev-parse HEAD`

git rebase --onto ${ontoValue} ${endingCommit} ${startingCommit}
git rebase HEAD ${destBranch}