[GSoC Update] The 7th week

Hi all,

    This is my status update of the 7th official week of GSoC.
    In the past week, I worked hard parallelly on two branches, one is
the parent rewrite feature and the other is the basic 'git-log -L'
problem fix. Generally:

    1. parent rewrite: I have finally figure out a version 1 of it and
submit it the list. It contain the basic support for '--graph' option
and I also add a few new test cases for it, also there is a little
document update;
    2. the 'git-log -L' basic feature: I have fixed 2 potential bugs
of it and also try to free the commit_list along with the
cmd_line_log_walk to try to reduce some memory leak.

    And there is an extra commit, which is a little bug fix of
previous 'diff-graph' series. :-)

    What's coming on:

Thanks!