provide a helper to set the commit buffer

Right now this is just a one-liner, but abstracting it will
make it easier to change later.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/blame.c

@@ -2046,7 +2046,7 @@ static struct commit *fake_working_tree_commit(struct diff_options *opt,
 		    ident, ident, path,
 		    (!contents_from ? path :
 		     (!strcmp(contents_from, "-") ? "standard input" : contents_from)));
-	commit->buffer = strbuf_detach(&msg, NULL);
+	set_commit_buffer(commit, strbuf_detach(&msg, NULL));
 
 	if (!contents_from || strcmp("-", contents_from)) {
 		struct stat st;

commit.c

@@ -245,6 +245,11 @@ int unregister_shallow(const unsigned char *sha1)
 	return 0;
 }
 
+void set_commit_buffer(struct commit *commit, void *buffer)
+{
+	commit->buffer = buffer;
+}
+
 void free_commit_buffer(struct commit *commit)
 {
 	free(commit->buffer);
@@ -335,7 +340,7 @@ int parse_commit(struct commit *item)
 	}
 	ret = parse_commit_buffer(item, buffer, size);
 	if (save_commit_buffer && !ret) {
-		item->buffer = buffer;
+		set_commit_buffer(item, buffer);
 		return 0;
 	}
 	free(buffer);

commit.h

@@ -51,6 +51,12 @@ int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long s
 int parse_commit(struct commit *item);
 void parse_commit_or_die(struct commit *item);
 
+/*
+ * Associate an object buffer with the commit. The ownership of the
+ * memory is handed over to the commit, and must be free()-able.
+ */
+void set_commit_buffer(struct commit *, void *buffer);
+
 /*
  * Free any cached object buffer associated with the commit.
  */

object.c

@@ -198,7 +198,7 @@ struct object *parse_object_buffer(const unsigned char *sha1, enum object_type t
 			if (parse_commit_buffer(commit, buffer, size))
 				return NULL;
 			if (!commit->buffer) {
-				commit->buffer = buffer;
+				set_commit_buffer(commit, buffer);
 				*eaten_p = 1;
 			}
 			obj = &commit->object;