gitk: Don't compare fake children when comparing commits
gitk: Don't compare fake children when comparing commits

This fixes a bug where the compare-commits function would advance
to a fake node (one representing local changes, either checked in
but not committed, or not checked in) and then get an error when
trying to get the patch-id.  This fixes it by only considering the
real children of each commit.

Reported-by: Stephen Rothwell <4bf0fb350827ce8d86875e76c923a478597c3cef@canb.auug.org.au>
Signed-off-by: Paul Mackerras <19a0ba370c443ba08d20b5061586430ab449ee8c@samba.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git