gitk: Fix missing commits when using -S or -G

When -S or -G is used as a filter option, the resulting commit list rarely contains all matching commits. Only a certain number of commits are displayed and the rest are missing. "git log --boundary -S" does not return as many boundary commits as you might expect. gitk makes up for this in closevarcs() by adding missing parent (boundary) commits. However, it does not change $numcommits, which limits how many commits are shown. In the end, some commits at the end of the commit list are simply not shown. Change $numcommits whenever a missing parent is added to the current view. Signed-off-by: Stefan Dotterweich <stefandotterweich@gmx.de> Signed-off-by: Paul Mackerras <paulus@ozlabs.org>