Add helper for diff line stats

This adds a `git_diff_patch_line_stats()` API that gets the total
number of adds, deletes, and context lines in a patch.  This will
make it a little easier to emulate `git diff --stat` and the like.

Right now, this relies on generating the `git_diff_patch` object,
which is a pretty heavyweight way to get stat information.  At
some future point, it would probably be nice to be able to get
this information without allocating the entire `git_diff_patch`,
but that's a much larger project.

1 files changed, 22 insertions, 0 deletions

diff --git a/include/git2/diff.h b/include/git2/diff.h
index c052f34f8..81c41df04 100644
--- a/include/git2/diff.h
+++ b/include/git2/diff.h
@@ -704,6 +704,28 @@ GIT_EXTERN(size_t) git_diff_patch_num_hunks(
 	git_diff_patch *patch);
 
 /**
+ * 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.
+ *
+ * @param total_context Count of context lines in output, can be NULL.
+ * @param total_additions Count of addition lines in output, can be NULL.
+ * @param total_deletions Count of deletion lines in output, can be NULL.
+ * @param patch The git_diff_patch object
+ * @return Number of lines in hunk or -1 if invalid hunk index
+ */
+GIT_EXTERN(int) git_diff_patch_line_stats(
+	size_t *total_context,
+	size_t *total_additions,
+	size_t *total_deletions,
+	const git_diff_patch *patch);
+
+/**
  * Get the information about a hunk in a patch
  *
  * Given a patch and a hunk index into the patch, this returns detailed