bisect: check ancestors without forking a "git rev-list" process

We must save the pending commits that will be used during revision
walking and unparse them after, because we want to leave a clean
state for the next revision walking that will try to find the best
bisection point.

As we don't fork a process anymore to call "git rev-list", we need
to remove the use of GIT_TRACE to check how "git rev-list" is
called from the t6030 test that uses it.
Signed-off-by: NChristian Couder <chriscool@tuxfamily.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

bisect.c

@@ -750,42 +750,31 @@ static void check_merge_bases(void)
 	free_commit_list(result);
 }
 
-/*
- * This function runs the command "git rev-list $_good ^$_bad"
- * and returns 1 if it produces some output, 0 otherwise.
- */
-static int check_ancestors(void)
+static int check_ancestors(const char *prefix)
 {
-	struct argv_array rev_argv = { NULL, 0, 0 };
-	struct strbuf str = STRBUF_INIT;
-	int i, result = 0;
-	struct child_process rls;
-	FILE *rls_fout;
+	struct rev_info revs;
+	struct object_array pending_copy;
+	int i, res;
 
-	argv_array_push(&rev_argv, xstrdup("rev-list"));
-	argv_array_push_sha1(&rev_argv, current_bad_sha1, "^%s");
-	for (i = 0; i < good_revs.sha1_nr; i++)
-		argv_array_push_sha1(&rev_argv, good_revs.sha1[i], "%s");
-	argv_array_push(&rev_argv, NULL);
+	bisect_rev_setup(&revs, prefix, "^%s", "%s", 0);
 
-	memset(&rls, 0, sizeof(rls));
-	rls.argv = rev_argv.argv;
-	rls.out = -1;
-	rls.git_cmd = 1;
-	if (start_command(&rls))
-		die("Could not launch 'git rev-list' command.");
-	rls_fout = fdopen(rls.out, "r");
-	while (strbuf_getline(&str, rls_fout, '\n') != EOF) {
-		strbuf_trim(&str);
-		if (*str.buf) {
-			result = 1;
-			break;
-		}
+	/* Save pending objects, so they can be cleaned up later. */
+	memset(&pending_copy, 0, sizeof(pending_copy));
+	for (i = 0; i < revs.pending.nr; i++)
+		add_object_array(revs.pending.objects[i].item,
+				 revs.pending.objects[i].name,
+				 &pending_copy);
+
+	bisect_common(&revs);
+	res = (revs.commits != NULL);
+
+	/* Clean up objects used, as they will be reused. */
+	for (i = 0; i < pending_copy.nr; i++) {
+		struct object *o = pending_copy.objects[i].item;
+		unparse_commit((struct commit *)o);
 	}
-	fclose(rls_fout);
-	finish_command(&rls);
 
-	return result;
+	return res;
 }
 
 /*
@@ -813,7 +802,8 @@ static void check_good_are_ancestors_of_bad(const char *prefix)
 	if (good_revs.sha1_nr == 0)
 		return;
 
-	if (check_ancestors())
+	/* Check if all good revs are ancestor of the bad rev. */
+	if (check_ancestors(prefix))
 		check_merge_bases();
 
 	/* Create file BISECT_ANCESTORS_OK. */

t/t6030-bisect-porcelain.sh

@@ -482,28 +482,17 @@ test_expect_success 'good merge bases when good and bad are siblings' '
 	git bisect reset
 '
 
-check_trace() {
-	grep "$1" "$GIT_TRACE" | grep "\^$2" | grep "$3" >/dev/null
-}
-
 test_expect_success 'optimized merge base checks' '
-	GIT_TRACE="$(pwd)/trace.log" &&
-	export GIT_TRACE &&
 	git bisect start "$HASH7" "$SIDE_HASH7" > my_bisect_log.txt &&
 	grep "merge base must be tested" my_bisect_log.txt &&
 	grep "$HASH4" my_bisect_log.txt &&
-	check_trace "rev-list" "$HASH7" "$SIDE_HASH7" &&
 	git bisect good > my_bisect_log2.txt &&
 	test -f ".git/BISECT_ANCESTORS_OK" &&
 	test "$HASH6" = $(git rev-parse --verify HEAD) &&
-	: > "$GIT_TRACE" &&
 	git bisect bad > my_bisect_log3.txt &&
-	test_must_fail check_trace "rev-list" "$HASH6" "$SIDE_HASH7" &&
 	git bisect good "$A_HASH" > my_bisect_log4.txt &&
 	grep "merge base must be tested" my_bisect_log4.txt &&
-	test_must_fail test -f ".git/BISECT_ANCESTORS_OK" &&
-	check_trace "rev-list" "$HASH6" "$A_HASH" &&
-	unset GIT_TRACE
+	test_must_fail test -f ".git/BISECT_ANCESTORS_OK"
 '
 
 # This creates another side branch called "parallel" with some files