def METHOD_NAME(filepath, since):
    """Get git commit hashes for `filepath` `since` a given date."""
    cmd = ('git', 'log', '--since="'+since+'"', '--pretty=format:%H',
           '--', filepath)
    stdout, stderr = execute(cmd)
    commits = []
    if stdout:
        commits = [c for c in stdout.split('\n') if c]
    return commits