Clean up diff implementation for review

This fixes several bugs, updates tests and docs, eliminates the
FILE* assumption in favor of printing callbacks for the diff patch
formatter helpers, and adds a "diff" example function that can
perform a diff from the command line.

1 files changed, 62 insertions, 0 deletions

diff --git a/tests-clar/diff/diff_helpers.c b/tests-clar/diff/diff_helpers.c
index b2dbe9ee..3fcf45c1 100644
--- a/tests-clar/diff/diff_helpers.c
+++ b/tests-clar/diff/diff_helpers.c
@@ -20,3 +20,65 @@ git_tree *resolve_commit_oid_to_tree(
 	git_object_free(obj);
 	return tree;
 }
+
+int diff_file_fn(
+	void *cb_data,
+	git_diff_delta *delta,
+	float progress)
+{
+	diff_expects *e = cb_data;
+	(void)progress;
+	e->files++;
+	if (delta->old_attr == 0)
+		e->file_adds++;
+	else if (delta->new_attr == 0)
+		e->file_dels++;
+	else
+		e->file_mods++;
+	return 0;
+}
+
+int diff_hunk_fn(
+	void *cb_data,
+	git_diff_delta *delta,
+	git_diff_range *range,
+	const char *header,
+	size_t header_len)
+{
+	diff_expects *e = cb_data;
+	(void)delta;
+	(void)header;
+	(void)header_len;
+	e->hunks++;
+	e->hunk_old_lines += range->old_lines;
+	e->hunk_new_lines += range->new_lines;
+	return 0;
+}
+
+int diff_line_fn(
+	void *cb_data,
+	git_diff_delta *delta,
+	char line_origin,
+	const char *content,
+	size_t content_len)
+{
+	diff_expects *e = cb_data;
+	(void)delta;
+	(void)content;
+	(void)content_len;
+	e->lines++;
+	switch (line_origin) {
+	case GIT_DIFF_LINE_CONTEXT:
+		e->line_ctxt++;
+		break;
+	case GIT_DIFF_LINE_ADDITION:
+		e->line_adds++;
+		break;
+	case GIT_DIFF_LINE_DELETION:
+		e->line_dels++;
+		break;
+	default:
+		break;
+	}
+	return 0;
+}