diffcore-order: export generic ordering interface

diffcore_order() interface only accepts a queue of `struct
diff_filepair`.

In the next patches, we'll want to order `struct combine_diff_path`
by path, so let's first rework diffcore-order to also provide
generic low-level interface for ordering arbitrary objects, provided
they have path accessors.

The new interface is:

    - `struct obj_order`    for describing objects to ordering routine, and
    - order_objects()       for actually doing the ordering work.

Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/diffcore.h b/diffcore.h
index 79de8cf28d..cbe9e62b49 100644
--- a/diffcore.h
+++ b/diffcore.h
@@ -109,6 +109,20 @@ extern void diffcore_merge_broken(void);
 extern void diffcore_pickaxe(struct diff_options *);
 extern void diffcore_order(const char *orderfile);
 
+/* low-level interface to diffcore_order */
+struct obj_order {
+	void *obj;	/* setup by caller */
+
+	/* setup/used by order_objects() */
+	int orig_order;
+	int order;
+};
+
+typedef const char *(*obj_path_fn_t)(void *obj);
+
+void order_objects(const char *orderfile, obj_path_fn_t obj_path,
+		   struct obj_order *objs, int nr);
+
 #define DIFF_DEBUG 0
 #if DIFF_DEBUG
 void diff_debug_filespec(struct diff_filespec *, int, const char *);