StartGenerator is responsible for propagating the RevWalk's
parent rewrite setting, but it currently only does so when a
non-default TreeFilter is set, when it should also do so if
the default TreeFilter is used with a non-default RevFilter.
Adding a new if condition within StartGenerator to enable parent
rewrite with non-default RevFilter.
TreeRevFilter relied on the old buggy functionality and has
been modified to explicitly refrain from rewriting parents.
Change-Id: I4e4ff67fb279edbcc3461496b132cea774fb742f