bisect: change calling-convention of `find_bisection()`

This function takes a commit list and returns a commit list. The
returned list is built by modifying the original list. Thus the caller
should not use the original list again (and after the next commit fixes
a memory leak, it must not).

Change the function signature so that it takes a **list and has void
return type. That should make it harder to misuse this function.

While we're here, document this function.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

bisect.c

@@ -360,21 +360,20 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 		return best_bisection_sorted(list, nr);
 }
 
-struct commit_list *find_bisection(struct commit_list *list,
-					  int *reaches, int *all,
-					  int find_all)
+void find_bisection(struct commit_list **commit_list, int *reaches,
+		    int *all, int find_all)
 {
 	int nr, on_list;
-	struct commit_list *p, *best, *next, *last;
+	struct commit_list *list, *p, *best, *next, *last;
 	int *weights;
 
-	show_list("bisection 2 entry", 0, 0, list);
+	show_list("bisection 2 entry", 0, 0, *commit_list);
 
 	/*
 	 * Count the number of total and tree-changing items on the
 	 * list, while reversing the list.
 	 */
-	for (nr = on_list = 0, last = NULL, p = list;
+	for (nr = on_list = 0, last = NULL, p = *commit_list;
 	     p;
 	     p = next) {
 		unsigned flags = p->item->object.flags;
@@ -402,7 +401,7 @@ struct commit_list *find_bisection(struct commit_list *list,
 		*reaches = weight(best);
 	}
 	free(weights);
-	return best;
+	*commit_list = best;
 }
 
 static int register_ref(const char *refname, const struct object_id *oid,
@@ -954,8 +953,7 @@ int bisect_next_all(const char *prefix, int no_checkout)
 
 	bisect_common(&revs);
 
-	revs.commits = find_bisection(revs.commits, &reaches, &all,
-				       !!skipped_revs.nr);
+	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr);
 	revs.commits = managed_skipped(revs.commits, &tried);
 
 	if (!revs.commits) {

bisect.h

@@ -1,9 +1,15 @@
 #ifndef BISECT_H
 #define BISECT_H
 
-extern struct commit_list *find_bisection(struct commit_list *list,
-					  int *reaches, int *all,
-					  int find_all);
+/*
+ * Find bisection. If something is found, `reaches` will be the number of
+ * commits that the best commit reaches. `all` will be the count of
+ * non-SAMETREE commits. If nothing is found, `list` will be NULL.
+ * Otherwise, it will be either all non-SAMETREE commits or the single
+ * best commit, as chosen by `find_all`.
+ */
+extern void find_bisection(struct commit_list **list, int *reaches, int *all,
+			   int find_all);
 
 extern struct commit_list *filter_skipped(struct commit_list *list,
 					  struct commit_list **tried,

builtin/rev-list.c

@@ -397,8 +397,7 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	if (bisect_list) {
 		int reaches = reaches, all = all;
 
-		revs.commits = find_bisection(revs.commits, &reaches, &all,
-					      bisect_find_all);
+		find_bisection(&revs.commits, &reaches, &all, bisect_find_all);
 
 		if (bisect_show_vars)
 			return show_bisect_vars(&info, reaches, all);