Get line counts of each type in a patch.
This helps imitate a diff --numstat type of output. For that purpose,
you only need the total_additions
and total_deletions
values, but we
include the total_context
line count in case you want the total number
of lines of diff output that will be generated.
All outputs are optional. Pass NULL if you don't need a particular count.
Count of context lines in output, can be NULL.
Count of addition lines in output, can be NULL.
Count of deletion lines in output, can be NULL.
0 on success, < 0 on error