set commit as head of branch code example

Example 1: git set head to commit

# Set a new HEAD to a branch
# Note that commit can be a commit hash or tag or another branch
git reset --hard $COMMIT

Example 2: set head of branch at specific commit

# You can make master point at a specific commit this way
git checkout master
git reset --hard <commit-hash>

# git reset --hard command will throw away any uncommitted changes 
# (i.e. those just in your working tree or the index).