t/helper: add 'pack-mtimes' test-tool

In the next patch, we will implement and test support for writing a
cruft pack via a special mode of `git pack-objects`. To make sure that
objects are written with the correct timestamps, and a new test-tool
that can dump the object names and corresponding timestamps from a given
`.mtimes` file.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -738,6 +738,7 @@ TEST_BUILTINS_OBJS += test-oid-array.o
 TEST_BUILTINS_OBJS += test-oidmap.o
 TEST_BUILTINS_OBJS += test-oidtree.o
 TEST_BUILTINS_OBJS += test-online-cpus.o
+TEST_BUILTINS_OBJS += test-pack-mtimes.o
 TEST_BUILTINS_OBJS += test-parse-options.o
 TEST_BUILTINS_OBJS += test-parse-pathspec-file.o
 TEST_BUILTINS_OBJS += test-partial-clone.o

t/helper/test-pack-mtimes.c

@@ -0,0 +1,56 @@
+#include "git-compat-util.h"
+#include "test-tool.h"
+#include "strbuf.h"
+#include "object-store.h"
+#include "packfile.h"
+#include "pack-mtimes.h"
+
+static void dump_mtimes(struct packed_git *p)
+{
+	uint32_t i;
+	if (load_pack_mtimes(p) < 0)
+		die("could not load pack .mtimes");
+
+	for (i = 0; i < p->num_objects; i++) {
+		struct object_id oid;
+		if (nth_packed_object_id(&oid, p, i) < 0)
+			die("could not load object id at position %"PRIu32, i);
+
+		printf("%s %"PRIu32"\n",
+		       oid_to_hex(&oid), nth_packed_mtime(p, i));
+	}
+}
+
+static const char *pack_mtimes_usage = "\n"
+"  test-tool pack-mtimes <pack-name.mtimes>";
+
+int cmd__pack_mtimes(int argc, const char **argv)
+{
+	struct strbuf buf = STRBUF_INIT;
+	struct packed_git *p;
+
+	setup_git_directory();
+
+	if (argc != 2)
+		usage(pack_mtimes_usage);
+
+	for (p = get_all_packs(the_repository); p; p = p->next) {
+		strbuf_addstr(&buf, basename(p->pack_name));
+		strbuf_strip_suffix(&buf, ".pack");
+		strbuf_addstr(&buf, ".mtimes");
+
+		if (!strcmp(buf.buf, argv[1]))
+			break;
+
+		strbuf_reset(&buf);
+	}
+
+	strbuf_release(&buf);
+
+	if (!p)
+		die("could not find pack '%s'", argv[1]);
+
+	dump_mtimes(p);
+
+	return 0;
+}

t/helper/test-tool.c

@@ -48,6 +48,7 @@ static struct test_cmd cmds[] = {
 	{ "oidmap", cmd__oidmap },
 	{ "oidtree", cmd__oidtree },
 	{ "online-cpus", cmd__online_cpus },
+	{ "pack-mtimes", cmd__pack_mtimes },
 	{ "parse-options", cmd__parse_options },
 	{ "parse-pathspec-file", cmd__parse_pathspec_file },
 	{ "partial-clone", cmd__partial_clone },

t/helper/test-tool.h

@@ -38,6 +38,7 @@ int cmd__mktemp(int argc, const char **argv);
 int cmd__oidmap(int argc, const char **argv);
 int cmd__oidtree(int argc, const char **argv);
 int cmd__online_cpus(int argc, const char **argv);
+int cmd__pack_mtimes(int argc, const char **argv);
 int cmd__parse_options(int argc, const char **argv);
 int cmd__parse_pathspec_file(int argc, const char** argv);
 int cmd__partial_clone(int argc, const char **argv);