<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def diff(context, file_name):
 """See changes that occured since last check in"""

    context.obj.find_repo_type()
    if context.obj.vc_name == 'git':
        context.obj.call(['git', 'diff', '--color-words',
                          '--ignore-space-change', file_name])
    elif context.obj.vc_name == 'hg':
        context.obj.call(['hg', 'diff', file_name])