"gitk --author=foo" shows also parent

Hi!

	$ gitk --author=foo

...seems to show also the parent of each author-matched commit, whereas

	$ git log --author=foo

does not. Is this intended or a bug? I've stumbled over this while configuring a gitk view with the author field.

Nikolai

# Setup ~/work/gitkBug % git init . ~/work/gitkBug % touch file1 file2 ~/work/gitkBug % git add file1 ~/work/gitkBug % git commit "--author=MrFoo <foo@world>" file1 -m "add file1" ~/work/gitkBug % git add file2 ~/work/gitkBug % git commit "--author=MrBar <bar@world>" file2 -m "add file2"

# TEST: git log --author - OK
~/work/gitkBug % git log --author=MrBar # OK, as expected
commit 8aa4a4f651162bcb2275a1e9ee23fc1bb7226097
Author: MrBar <bar@world>
Date:   Tue Apr 26 14:22:58 2016 +0200

     add file2

# TEST: gitk --author - OPS ~/work/gitkBug % gitk --author=MrBar # Ops, gitk shows also the parent commit