gitstats: Bugfix for commitdiffMatches
When retreiving the log, the -U0 option was not passed,
which caused the lines around the change to be matches on
too. As a result, a commit was also marked as 'matching' if
it made a change near a matching line.
Not only that, but there was no check in place to check for
the commits without parents either.
Finally, the biggest error was that instead of setting the
'addIt' variable to False, the 'addit' variable was set,
which is not used, and so all commits matched.
Bug-introduced-in:
56a92410fe3977528673af70f42371bf76e9cab5