Fix the examples/diff.c implementation of the -B and added new helper functions to extract options.
Fix the examples/diff.c implementation of the -B and added new helper functions to extract options.

Fixed the examples/diff.c implementation of -B options and added new helper function to extract the option values.

saurabhsuniljain/libgit2,saurabhsuniljain/libgit2,saurabhsuniljain/libgit2,saurabhsuniljain/libgit2,saurabhsuniljain/libgit2,saurabhsuniljain/libgit2