notes: convert combine_notes_* to object_id

Convert the definition and declarations of combine_notes_* functions
to struct object_id and adjust usage of these functions.

Signed-off-by: Patryk Obara <patryk.obara@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

notes.h

@@ -9,27 +9,32 @@
  * When adding a new note annotating the same object as an existing note, it is
  * up to the caller to decide how to combine the two notes. The decision is
  * made by passing in a function of the following form. The function accepts
- * two SHA1s -- of the existing note and the new note, respectively. The
+ * two object_ids -- of the existing note and the new note, respectively. The
  * function then combines the notes in whatever way it sees fit, and writes the
- * resulting SHA1 into the first SHA1 argument (cur_sha1). A non-zero return
+ * resulting oid into the first argument (cur_oid). A non-zero return
  * value indicates failure.
  *
- * The two given SHA1s shall both be non-NULL and different from each other.
- * Either of them (but not both) may be == null_sha1, which indicates an
- * empty/non-existent note. If the resulting SHA1 (cur_sha1) is == null_sha1,
+ * The two given object_ids shall both be non-NULL and different from each
+ * other. Either of them (but not both) may be == null_oid, which indicates an
+ * empty/non-existent note. If the resulting oid (cur_oid) is == null_oid,
  * the note will be removed from the notes tree.
  *
  * The default combine_notes function (you get this when passing NULL) is
  * combine_notes_concatenate(), which appends the contents of the new note to
  * the contents of the existing note.
  */
-typedef int (*combine_notes_fn)(unsigned char *cur_sha1, const unsigned char *new_sha1);
+typedef int (*combine_notes_fn)(struct object_id *cur_oid,
+				const struct object_id *new_oid);
 
 /* Common notes combinators */
-int combine_notes_concatenate(unsigned char *cur_sha1, const unsigned char *new_sha1);
-int combine_notes_overwrite(unsigned char *cur_sha1, const unsigned char *new_sha1);
-int combine_notes_ignore(unsigned char *cur_sha1, const unsigned char *new_sha1);
-int combine_notes_cat_sort_uniq(unsigned char *cur_sha1, const unsigned char *new_sha1);
+int combine_notes_concatenate(struct object_id *cur_oid,
+			      const struct object_id *new_oid);
+int combine_notes_overwrite(struct object_id *cur_oid,
+			    const struct object_id *new_oid);
+int combine_notes_ignore(struct object_id *cur_oid,
+			 const struct object_id *new_oid);
+int combine_notes_cat_sort_uniq(struct object_id *cur_oid,
+				const struct object_id *new_oid);
 
 /*
  * Notes tree object