Add note about git log options

[rgaiacs]

Address #745.

@drj11 and @jiffyclub Could you review this?

[jiffyclub]

--oneline is probably the most useful option at this point, maybe start with just that?

[rgaiacs]

--oneline is probably the most useful option at this point, maybe start with just that?

I don't want to expand this note too much. I hope that instructors already had
taught git help at this point so students can git help log and read what
--oneline, --graph, ... are for.

If more people believe that the write version of the lesson should have this
incremental mention of options I'm OK in change the PR.

[jiffyclub]

Sorry, I meant that I think we ought to mention only --oneline and none of the other options.

[rgaiacs]

@jiffyclub Could you take a look on f162d28?

[rgaiacs]

@jiffyclub I'm OK to add a note remember students to check --graph at novice/git/03-conflict.md but at this lesson we don't have a example of git log. Will be a little time consuming for me do this change during this split repo thing so could you (1) merge this PR as it is and after #759 I will find some time to improve novice/git/03-conflict.md or (2) could you close this PR and I will create a new one after #759?

[jiffyclub]

Okay, let's close this for now and revisit after we break apart the repo. We'll have #745 to remind us.