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.

2 files changed, 40 insertions, 1 deletions

diff --git a/src/buffer.h b/src/buffer.h
index 4efd240b5..6e73895b4 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -134,6 +134,13 @@ GIT_INLINE(ssize_t) git_buf_rfind(git_buf *buf, char ch)
 	return idx;
 }
 
+GIT_INLINE(ssize_t) git_buf_find(git_buf *buf, char ch)
+{
+	size_t idx = 0;
+	while (idx < buf->size && buf->ptr[idx] != ch) idx++;
+	return (idx == buf->size) ? -1 : (ssize_t)idx;
+}
+
 /* Remove whitespace from the end of the buffer */
 void git_buf_rtrim(git_buf *buf);
 
diff --git a/src/diff_output.c b/src/diff_output.c
index 8a7a7a2a1..4f1064b7f 100644
--- a/src/diff_output.c
+++ b/src/diff_output.c
@@ -1501,6 +1501,39 @@ size_t git_diff_patch_num_hunks(git_diff_patch *patch)
 	return patch->hunks_size;
 }
 
+int git_diff_patch_line_stats(
+	size_t *total_ctxt,
+	size_t *total_adds,
+	size_t *total_dels,
+	const git_diff_patch *patch)
+{
+	size_t totals[3], idx;
+
+	memset(totals, 0, sizeof(totals));
+
+	for (idx = 0; idx < patch->lines_size; ++idx) {
+		switch (patch->lines[idx].origin) {
+		case GIT_DIFF_LINE_CONTEXT:  totals[0]++; break;
+		case GIT_DIFF_LINE_ADDITION: totals[1]++; break;
+		case GIT_DIFF_LINE_DELETION: totals[2]++; break;
+		default:
+			/* diff --stat and --numstat don't count EOFNL marks because
+			 * they will always be paired with a ADDITION or DELETION line.
+			 */
+			break;
+		}
+	}
+
+	if (total_ctxt)
+		*total_ctxt = totals[0];
+	if (total_adds)
+		*total_adds = totals[1];
+	if (total_dels)
+		*total_dels = totals[2];
+
+	return 0;
+}
+
 int git_diff_patch_get_hunk(
 	const git_diff_range **range,
 	const char **header,
@@ -1706,4 +1739,3 @@ int git_diff__paired_foreach(
 
 	return 0;
 }
-